Devices and methods for performing knee arthroplasty

ABSTRACT

Methods and devices for performing knee arthroplasty including but not limited to bicruciate retaining knee arthroplasty are provided. Methods and devices for preparing a proximal tibia for a tibial implant are also provided. These methods and devices, in at least some embodiments and uses, facilitate decreasing the complexity of knee arthroplasty procedures such as bicruciate retaining procedures while maintaining, if not improving on, the safety, accuracy and/or effectiveness of such procedures.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application claims the benefit of U.S. Provisional PatentApplication Ser. No. 61/552,321 filed Oct. 27, 2011, the contents ofwhich are incorporated herein by reference in their entirety.

FIELD OF THE INVENTION

The present invention relates generally to surgical devices and methods,and more particularly relates to orthopaedic devices and methods forperforming knee arthroplasty.

BACKGROUND

Total knee arthroplasty procedures often require the sacrifice of theanterior cruciate ligament (ACL) and/or the posterior cruciate ligament(PCL). As such, total knee prostheses often include structures andmechanisms that attempt to provide the same or similar functionsprovided by the ACL and PCL. However, these conventional total kneeprostheses may not fully replicate the normal proprioception,kinematics, and/or biomechanical functions provided by naturalligaments. Bicruciate retaining knee replacements have been used in thepast, but were associated with problems of knee stiffness and implantfailure that were likely attributable to inadequate implant design,instrumentation, and/or implantation technique. Accordingly, there is adesire in some cases to preserve functioning cruciate ligaments in youngand active patients who require knee joint replacement, to maintain anatural feeling, and normal biomechanical function and performance ofthe knee after total knee replacement. There is also a desire for moreefficient and accurate devices and methods for preparing femurs andtibias for bicruciate retaining implants (i.e., ACL and PCL preservingimplants), as well as other types of knee implants, since many kneeprocedures (especially, but not limited to, bicruciate retainingprocedures) often utilize devices and methods that are less than ideal.

Thus, there remains a need to provide improved devices and methods forperforming knee arthroplasty. The present invention satisfies this needand provides other benefits and advantages in a novel and unobviousmanner.

SUMMARY

While the actual nature of the invention covered herein can only bedetermined with reference to the claims appended hereto, certain formsof the invention that are characteristic of the embodiments disclosedherein are described briefly as follows.

Devices and methods for performing knee arthroplasty procedures areprovided, including device and methods used in association with totalknee arthroplasty (TKA) procedures and techniques including, forexample, procedures and techniques such as bicruciate retainingarthroplasty, as well as other procedures and techniques describedherein.

In one form of the invention, instrumentation is provided for resectionof the proximal tibia. The instrumentation includes a mounting baseadapted for coupling to the proximal tibia, a cutting guide extendinglaterally from the mounting base and including a lateral guide channelarranged along a cutting plane and dimensioned to guide a cutting devicegenerally along the cutting plane to form a resection cut in theproximal tibia, and an elongate pin interconnected with a mountingportion of the instrument and dimensioned for receipt within an openingin the proximal tibia, the elongate pin positioned adjacent the lateralguide channel within the cutting plane to thereby limit lateraldisplacement of the cutting device within the lateral guide channelalong the cutting plane.

In another form of the invention, instrumentation is provided forresection of the proximal tibia. The instrumentation includes a cuttingdevice, a mount device configured for attachment to the proximal tibiaand including a generally planar reference member extending along areference plane, a mounting base releasably lockable to the planarreference member of the mount device, a cutting guide extendinglaterally from the mounting base and including a lateral guide channelarranged along a cutting plane and dimensioned to guide the cuttingdevice generally along the cutting plane to form a resection cut in theproximal tibia, and an elongate pin pivotally connected to either themounting base or the cutting guide and configured for pivotal movementgenerally along the cutting plane, the elongate pin dimensioned forreceipt within an opening in the proximal tibia, the elongate pinpositioned adjacent the lateral guide channel within the cutting planeto thereby limit lateral displacement of the cutting device within thelateral guide channel along the cutting plane.

In another form of the invention, a method is provided for resection ofthe proximal tibia. The method includes the steps of providing aninstrument including a cutting guide and an elongate pin, the cuttingguide defining a lateral guide channel extending along a cutting plane,the elongate pin interconnected with a mounting portion of theinstrument and positioned adjacent the lateral guide channel within thecutting plane, inserting the elongate pin into an opening in theproximal tibia, mounting the instrument to the proximal tibia, guiding acutting device through the lateral guide channel generally along thecutting plane to form a resection cut in the proximal tibia, andlimiting displacement of the cutting device within the lateral guidechannel laterally beyond the elongate pin to control a lateral depth ofthe resection cut in the proximal tibia.

It is one object of the present invention to provide improvedorthopaedic devices and methods for performing knee arthroplasty.Further embodiments, forms, features, aspects, benefits, objects, andadvantages of the present invention will become apparent from thedetailed description and figures provided herewith.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a distal portion of a femur bone.

FIG. 2 illustrates a proximal portion of a tibia bone.

FIG. 3 illustrates a resected distal portion of a femur bone.

FIG. 4 illustrates a femoral trial component attached to the resecteddistal portion of the femur bone of FIG. 3.

FIG. 5 illustrates a datum block according to one form of the invention,as shown in relation to the proximal tibia.

FIG. 6A illustrates a left side view of the datum block of FIG. 5.

FIG. 6B illustrates a right side view of the datum block of FIG. 5.

FIG. 6C illustrates an anterior end view of the datum block of FIG. 5.

FIG. 6D illustrates a bottom view of the datum block of FIG. 5.

FIG. 6E illustrates a top view of the datum block of FIG. 5.

FIG. 6F illustrates a posterior end view of the datum block of FIG. 5.

FIG. 7A illustrates an unlocked configuration of the datum block of FIG.5.

FIG. 7B illustrates a locked configuration of the datum block of FIG. 5.

FIG. 8A illustrates one embodiment of a locking mechanism used inassociation with the datum block of FIG. 7A, as shown in an unlockedconfiguration.

FIG. 8B illustrates the locking mechanism of FIG. 8A, as shown in alocked configuration.

FIG. 9 illustrates the datum block of FIG. 5 provisionally attached tothe proximal tibia by a provisional attachment pin.

FIG. 10 illustrates the datum block of FIG. 5 terminally attached to theproximal tibia by terminal attachment pins.

FIG. 11 illustrates a depth stylus according to one form of theinvention, as shown attached to the datum block of FIG. 5 in relation tothe proximal tibia.

FIG. 12 illustrates a perspective view of the depth stylus of FIG. 11.

FIG. 13A illustrates a left side view of the depth stylus of FIG. 11.

FIG. 13B illustrates a right side view of the depth stylus of FIG. 11.

FIG. 13C illustrates a bottom view of the depth stylus of FIG. 11.

FIG. 13D illustrates an anterior end view of the depth stylus of FIG.11.

FIG. 14 illustrates one embodiment of an adjustment mechanism used inassociation with the depth stylus of FIG. 11.

FIG. 15 illustrates a second operational position of the depth stylus ofFIG. 11.

FIG. 16A illustrates an alternative operational configuration of thedepth stylus of FIG. 11, as shown in a first operational position inrelation to the proximal tibia.

FIG. 16B illustrates an alternative operational configuration of thedepth stylus of FIG. 11, as shown in a second operational position inrelation to the proximal tibia.

FIG. 17A illustrates an eminence stylus according to one form of theinvention, as shown attached to the datum block of FIG. 5 in relation tothe proximal tibia.

FIG. 17B illustrates an eminence stylus according to another form of theinvention, as shown attached to the proximal tibia.

FIG. 18A illustrates a left side view of the eminence stylus of FIG.17A.

FIG. 18B illustrates a right side view of the eminence stylus of FIG.17A.

FIG. 18C illustrates an anterior end view of the eminence stylus of FIG.17A.

FIG. 18D illustrates a top view of the eminence stylus of FIG. 17A.

FIG. 18E illustrates a bottom view of the eminence stylus of FIG. 17A.

FIG. 18F illustrates a posterior end view of the eminence stylus of FIG.17A.

FIG. 19A illustrates a perspective view of the eminence stylus of FIG.17A in a first operational position.

FIG. 19B illustrates a perspective view of the eminence stylus of FIG.17A in a second operational position.

FIG. 19C illustrates a perspective view of the eminence stylus of FIG.17A in a third operational position.

FIG. 19D illustrates a top view of the first operational position of theeminence stylus of FIG. 19A.

FIG. 19E illustrates a top view of the second operational position ofthe eminence stylus of FIG. 19B.

FIG. 20A illustrates the eminence stylus of FIG. 17A in relation to thedatum block of FIG. 5 in preparation for medial resection of theproximal tibia.

FIG. 20B illustrates the eminence stylus of FIG. 17A locked to the datumblock of FIG. 5 and pinned to the proximal tibia in relation to themedially resected proximal tibia.

FIG. 20C illustrates the datum block of FIG. 5 in relation to themedially resected proximal tibia with the eminence stylus of FIG. 17Aremoved from the datum block.

FIG. 21A illustrates an anterior end view of an eminence stylusaccording to another form of the invention.

FIG. 21B illustrates a top view of the eminence stylus of FIG. 21A.

FIG. 22 illustrates the eminence stylus of FIGS. 21A and 21B locked tothe datum block of FIG. 5.

FIG. 23 illustrates a graduated tibial pin according to one form of theinvention.

FIG. 24A illustrates the graduated tibial pin of FIG. 23, as shownrelative to the eminence stylus of FIG. 17A locked to the datum block ofFIG. 5, all shown in relation to the proximal tibia.

FIG. 24B illustrates the graduated tibial pin of FIG. 23, as shownengaged with the eminence stylus and anchored in the proximal tibia.

FIG. 24C illustrates the graduated tibial pin of FIG. 23, as shownengaged with the eminence stylus and anchored in the proximal tibia inrelation to the medially resected proximal tibia.

FIG. 25A illustrates a superior view of FIG. 24A.

FIG. 25B illustrates a superior view of FIG. 24B.

FIG. 25C illustrates a superior view of FIG. 24C.

FIG. 26 illustrates a lateral cut guide according to one form of theinvention, as shown attached to the datum block of FIG. 5.

FIG. 27 illustrates a perspective view of the lateral cut guide of FIG.26.

FIG. 28A illustrates a top view of the lateral cut guide of FIG. 27.

FIG. 28B illustrates an anterior view of the lateral cut guide of FIG.27.

FIG. 29A illustrates a superior view of FIG. 26.

FIG. 29B illustrates a superior view of FIG. 26 following lateralresection of the proximal tibia and removal of the lateral bonefragment.

FIG. 30 illustrates a saw capture block according to one form of theinvention, as shown attached to the datum block of FIG. 5.

FIG. 31 illustrates a perspective view of the saw capture block of FIG.30.

FIG. 32A illustrates an anterior end view of the saw capture block ofFIG. 31.

FIG. 32B illustrates a bottom view of the saw capture block of FIG. 31.

FIG. 33A illustrates a left side view of FIG. 30.

FIG. 33B illustrates a top view of FIG. 30.

FIG. 33C illustrates an anterior end view of FIG. 30.

FIG. 34 illustrates a recut block according to one form of theinvention, as shown terminally attached to the proximal tibia byterminal attachment pins in relation to the medially resected proximaltibia.

FIG. 35 illustrates a side view of FIG. 34.

FIG. 36A illustrates a left side view of the recut block of FIG. 34.

FIG. 36B illustrates a right side view of the recut block of FIG. 34.

FIG. 36C illustrates an anterior end view of the recut block of FIG. 34.

FIG. 36D illustrates a bottom view of the recut block of FIG. 34.

FIG. 36E illustrates a top view of the recut block of FIG. 34.

FIG. 36F illustrates a posterior end view of the recut block of FIG. 34.

FIG. 37A illustrates an unlocked configuration of the recut block ofFIG. 34.

FIG. 37B illustrates a locked configuration of the recut block of FIG.34.

FIG. 38A illustrates one embodiment of a locking mechanism used inassociation with the recut block of FIG. 37A, as shown in an unlockedconfiguration.

FIG. 38B illustrates the locking mechanism of FIG. 38A, as shown in alocked configuration.

FIG. 39A illustrates one embodiment of a threaded member used inassociation with the locking mechanism of FIGS. 38A and 38B.

FIG. 39B illustrates one embodiment of a gripper member used inassociation with the locking mechanism of FIGS. 38A and 38B.

FIG. 39C illustrates a bottom view the locking mechanism of FIGS. 38Aand 38B.

FIG. 39D illustrates an end view the locking mechanism of FIGS. 38A and38B.

FIG. 40 illustrates a tibia size gauge according to one form of theinvention, as shown relative to the datum block of FIG. 5 and theeminence stylus of FIG. 17A, all shown in relation to the proximaltibia.

FIG. 41A illustrates a first operational position of the tibia sizegauge of FIG. 40, as shown in relation to the eminence stylus and theunresected medial region of the proximal tibia.

FIG. 41B illustrates the tibia size gauge of FIG. 40, as shown inrelation to a medial portion of a tibial baseplate.

FIG. 41C illustrates the tibial baseplate of FIG. 41B engaged to theresected proximal tibia.

FIG. 42A illustrates a second operational position of the tibia sizegauge of FIG. 40, as shown in relation to the eminence stylus and theunresected lateral region of the proximal tibia.

FIG. 42B illustrates the tibia size gauge of FIG. 40, as shown inrelation to a lateral portion of a tibial baseplate.

FIG. 42C illustrates the tibial baseplate of FIG. 42B engaged to theresected proximal tibia.

FIG. 43 illustrates a tibia size gauge according to another form of theinvention, including a gauge pointer engaged with another embodiment ofan eminence stylus locked to the datum block of FIG. 5 in relation tothe proximal tibia.

FIG. 44A illustrates a perspective view of the gauge pointer of FIG. 43.

FIG. 44B illustrates a perspective view of the eminence stylus of FIG.43.

FIG. 45A illustrates an anterior end view of the tibia size gauge ofFIG. 43.

FIG. 45B illustrates a top view of the tibia size gauge of FIG. 43, asshown in relation to the proximal tibia.

FIG. 46 illustrates a tibia rotation gauge according to one form of theinvention.

FIG. 47A illustrates the eminence stylus of FIG. 17A attached to thedatum block of FIG. 5, as shown in a first misaligned rotationalorientation relative to the proximal tibia.

FIG. 47B illustrates the eminence stylus of FIG. 17A attached to thedatum block of FIG. 5, as shown in a second misaligned rotationalorientation relative to the proximal tibia.

FIG. 48 illustrates the tibia rotation gauge of FIG. 46 engaged with theeminence stylus and the anterior surface of the proximal tibia tocorrect the misaligned rotational orientations shown in FIGS. 47A and47B.

FIG. 49 illustrates the tibia rotation gauge of FIG. 46 engaged with theanterior surface of the proximal tibia to correct the misalignedrotational orientations shown in FIGS. 47A and 47B.

FIG. 50 illustrates the tibia rotation gauge of FIG. 46 engaged with ananterior surface of a tibial baseplate.

FIG. 51 illustrates a schematic illustration of the tibia rotation gaugeof FIG. 46 engaged with an anterior surface of a set of tibialbaseplates having varying sizes.

FIG. 52 illustrates a perspective view of a tibia insert trial accordingto one form of the invention.

FIG. 53 illustrates an exploded view of the tibia insert trial of FIG.52.

FIG. 54 illustrates a bottom view of the main body component of thetibia insert trial of FIG. 52.

FIG. 55A illustrates a femoral trial component attached to the resecteddistal femur in relation to the medially resected proximal tibia.

FIG. 55B illustrates a femoral trial component attached to the resecteddistal femur in relation to the medially and laterally resected proximaltibia.

FIG. 56A illustrates a first operational position of the tibia inserttrial of FIG. 52 inserted between the femoral trial component and themedially resected proximal tibia of FIG. 55A.

FIG. 56B illustrates a second operational position of the tibia inserttrial of FIG. 52 inserted between the femoral trial component and themedially and laterally resected proximal tibia of FIG. 55B.

FIG. 57 illustrates a perspective view of a tibia size templateaccording to one form of the invention.

FIG. 58A illustrates a superior view of the tibia size template of FIG.57.

FIG. 58B illustrates an inferior view of the tibia size template of FIG.57.

FIG. 59A illustrates a first operational position of the tibia sizetemplate of FIG. 57, as shown in relation to the medially resectedproximal tibia.

FIG. 59B illustrates a second operational position of the tibia sizetemplate of FIG. 57, as shown in relation to the medially and laterallyresected proximal tibia.

FIG. 60A illustrates a superior view of FIG. 59A.

FIG. 60B illustrates a superior view of FIG. 59B.

FIG. 61A illustrates a perspective view of an anterior chisel accordingto one form of the invention.

FIG. 61B illustrates another perspective view of the anterior chisel ofFIG. 61A.

FIG. 62A illustrates the anterior chisel shown in FIG. 61A in relationto the medially and laterally resected proximal tibia.

FIG. 62B illustrates the anterior chisel shown in FIG. 61B in relationto the medially and laterally resected proximal tibia.

FIG. 63A illustrates a left side view of FIG. 62A.

FIG. 63B illustrates a left side view of FIG. 62B.

FIG. 64A illustrates a perspective view of the proximal tibia followingformation of a vertical cut into the tibial eminence resulting from thecutting step shown in FIGS. 62A and 63A.

FIG. 64B illustrates a perspective view of the proximal tibia followingformation of a horizontal cut into the tibial eminence resulting fromthe cutting step shown in FIGS. 62B and 63B.

FIG. 64C illustrates a perspective view of the proximal tibia followingformation of the vertical and horizontal cuts into the tibial eminenceand removal of the superior/anterior portion of the tibial eminence.

FIG. 65 illustrates a perspective view of a keel cavity formationinstrument according to one form of the invention.

FIG. 66 illustrates an exploded view of the keel cavity formationinstrument of FIG. 65.

FIG. 67 illustrates a left side view of the keel cavity formationinstrument of FIG. 65.

FIG. 68 illustrates a tibial baseplate trial for use in association withthe keel cavity formation instrument of FIG. 65, as shown engaged withthe medially and laterally resected proximal tibia and with thesuperior/anterior portion of the tibial eminence removed from theproximal tibia.

FIG. 69 illustrates the keel cavity formation instrument of FIG. 65engaged with the tibial baseplate trial of FIG. 68 in relation to thedistal femur and the proximal tibia.

FIG. 70A illustrates a first operational position of the keel cavityformation instrument of FIG. 65 for forming medial and lateral keelslots in the medially and laterally resected surfaces of the proximaltibia.

FIG. 70B illustrates a second operational position of the keel cavityformation instrument of FIG. 65 for forming an anterior keel slot in theanterior resected surface of the proximal tibia.

FIG. 70C illustrates a third operational position of the keel cavityformation instrument of FIG. 65 for forming clearance openings in theproximal tibia at locations between the medial and lateral keel slotsand the anterior keel slot.

FIG. 71A illustrates a superior view of the proximal tibia followingformation of the medial and lateral keel slots in the medially andlaterally resected surfaces of the proximal tibia.

FIG. 71B illustrates a superior view of the proximal tibia followingformation of the anterior keel slot in the anterior resected surface ofthe proximal tibia.

FIG. 71C illustrates a superior view of the proximal tibia followingformation of the clearance openings in the proximal tibia at locationsbetween the medial and lateral keel slots and the anterior keel slot.

FIG. 72A illustrates a perspective view of an anterior tibial gaugeaccording to one form of the invention.

FIG. 72B illustrates another perspective view of the anterior tibialgauge of FIG. 72A.

FIG. 73A illustrates a perspective view of a tibial baseplate trialaccording to one form of the invention engaged with the resectedproximal tibia.

FIG. 73B is a superior view of FIG. 73A.

FIG. 74A illustrates a perspective view of the anterior tibial gauge ofFIG. 72A engaged with the tibial baseplate trial of FIG. 73A in relationto the resected tibial eminence of the proximal tibia.

FIG. 74B is a superior view of FIG. 74A.

DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS

For the purpose of promoting an understanding of the principles of thepresent invention, reference will now be made to the embodimentsillustrated in the drawings and specific language will be used todescribe the same. It will nevertheless be understood that no limitationof the scope of the invention is hereby intended. Any alterations andfurther modifications in the described embodiments, and any furtherapplications of the principles of the invention as described herein arecontemplated as would normally occur to one skilled in the art to whichthe invention relates.

The following descriptions and illustrations of non-limiting embodimentsof the present invention are exemplary in nature, it being understoodthat the descriptions and illustrations related thereto are in no wayintended to limit the inventions disclosed herein and/or theirapplications and uses. Certain features and details associated withother embodiments of devices and methods that may be used in associationwith the present invention are found in commonly owned U.S. patentapplication Ser. No. 12/790,137 filed on May 28, 2010, which claims thebenefit of U.S. Provisional Patent Application Ser. No. 61/182,435 filedMay 29, 2009 and U.S. Provisional Patent Application Ser. No. 61/299,835filed Jan. 29, 2010, the contents of each application incorporatedherein by reference in their entirety.

In total knee arthroplasty procedures, various devices and methods areused in the preparation of a distal portion of a femur for receipt of afemoral implant, and in the preparation of a proximal portion of a tibiafor receipt of a tibial implant. The primary focus of this applicationis on devices and methods used in the preparation of the proximal tibia.However, other devices and methods used in the preparation of a distalfemur which may also be used in association with the present inventionare found in U.S. patent application Ser. No. 12/790,137, the contentsof which have been incorporated herein by reference in their entirety.

There is a strong relationship between femoral attachment locations ofsoft tissues and the articulation between the tibia and the femur. As ageneral matter, it can be shown that for knee implant designs relyingmore on contrived means of kinematic control and stability rather thanon the native soft tissue structures, kinematic patient outcomes areless sensitive to mismatch between, for instance, the inferior/superiorposition of the native femoral articular surfaces and the implantedfemoral articular surfaces, although such mismatches can still besignificant in some instances. However, when more native structures arepreserved in order to provide kinematic control and stability (e.g.,with bi-cruciate retaining implants), the preservation of the femoraljoint line can sometimes become more important to patient outcome.

Currently, the common practice is to favor resection of the distal femurto the level of the trochlea, rather than by measuring a resection depthfrom the medial femoral condyle. However, it may be preferable in atleast some cases to utilize methods and apparatus that counteract anytendency to resect the distal femur at a level other than the thicknessof the distal femoral implant. For example, it may be preferable toresect an amount equivalent to the thickness of the distal femoralimplant as measured from the distal medial (and/or lateral) condyle,which may better account for the mesial attachment sites on the femur ofthe posterior and/or anterior cruciate ligaments. It may also bepreferable in at least some cases to utilize methods and apparatus thatallow for early trialing and assessment of extension space and laxity.

Some methodologies associated with total knee arthroplasty proceduresalso reduce complications by not solving for femoral and tibial degreesof freedom simultaneously, but instead preparing the femur first andthen subsequently preparing the tibia. By completing all of the femoralresections prior to the tibial resections, the surgeon is provided witha fixed set of values from which he or she can determine the remainingtibial degrees of freedom. Another benefit of preparing the femur firstprovided by some of the methodologies associated with total kneearthroplasty procedures is that they ensure proper kinematics. Forproper kinematics, the femoral implant should generally conform to andarticulate with the native anatomy well (e.g., natural soft tissues andnative tibial cartilage). By separating the femoral resection steps fromthe tibial resection steps, the surgeon has no other input variableswith which to make femoral resection decisions other than inputvariables provided by the native femoral anatomy. A further benefit ofpreparing the distal femur before the proximal tibia is that a surgeonstill has the flexibility of performing a posterior stabilized, cruciateretaining surgery or a bicruciate retaining surgery with little or notime penalty or bone loss, even after the femoral side has beenprepared. Many of the devices and methods described below, however, arenot limited to only femur first techniques, or techniques that achieveall of the above benefits.

The following description and figures set forth a total kneearthroplasty procedure including preparation of the distal portion ofthe femur first, followed by subsequent preparation of the proximalportion of the tibia. By way of example, a distal portion 10 of thefemur is shown in FIG. 1, and a proximal portion 12 of the tibia isshown in FIG. 2 illustrating the tibial eminence region 14, the medialtibial plateau region 16 a, and the lateral tibial plateau region 16 b,each shown prior to preparation for receipt of femoral and tibialimplant components.

As should be appreciated, the distal femur 10 may be prepared usingvarious cutting instruments, trials, and other devices, examples ofwhich are disclosed in U.S. patent application Ser. No. 12/790,137, thecontents of which have been incorporated herein by reference in theirentirety. One example of a prepared distal femur 10 is illustrated inFIG. 3. Additionally, FIG. 4 illustrates one embodiment of a femoraltrial component 18 that may be attached to the prepared distal femur 10prior to preparation of the proximal tibia 12. However, it should beunderstood that the shape and configuration of the prepared distal femur10 and the femoral trial component 18 are exemplary in nature and do notlimit the scope of the invention.

Following preparation of the distal femur 10, the proximal tibia 12 isprepared using the following devices and methods according to variousembodiments of the present invention. However, it should be understoodthat the devices and methods of the present invention may be used intotal knee arthroplasty procedures including simultaneous or alternatingpreparation of the distal femur 10 and the proximal tibia 12, or intotal knee arthroplasty procedures where preparation of the proximaltibia 12 occurs first followed by preparation of the distal femur 10.

One problem faced when performing bicruciate-retaining TKA proceduresthat is of potential significance to at least some of the embodimentsdescribed herein is the complexity of the tibial resections. Thiscomplexity stems from at least two factors relating to the preservationof the cruciate ligaments.

A first factor is that there are more important degrees of freedomrelating to bicruciate-retaining arthroplasty procedures than isapparent for typical posterior-stabilized or PCL-retaining arthroplastyprocedures. For instance, in total knee arthroplasty, objects such asresection guides and other instrumentation in three-dimensional spacehave six degrees of freedom, including three translational degrees offreedom and three rotational degrees of freedom. At least fouradditional variables or “forms” may also apply in TKA procedures,including femoral implant size, tibial implant size, tibial insertthickness, and tibial insert articular shape. For a posterior-stabilizedor cruciate-retaining arthroplasty procedure, only three degrees offreedom (one translational and two rotational) are usually consideredimportant. For many, although not necessarily all, bicruciate-retainingarthroplasty procedures, there are at least three additional degrees offreedom which are considered important (i.e., one translational, onerotational, and one “form”). These three additional degrees of freedomarise due to constraints imposed by preservation of the tibial eminenceto which the cruciate ligaments are attached.

A second factor of potential relevance is that bicruciate retaining kneearthroplasty requires precise surgical techniques. The trade off with abicruciate-retaining technique is that of an increased risk ofmechanical complications such as stiffness, instability, fracture orimplant loosening due to the complexity of the surgery, in exchange forincreased postoperative patient mobility and function. A bicruciateretaining technique therefore requires more decisions to fix additionaldegrees of freedom, as well as a greater degree of decision accuracy inorder to mitigate the increased risks as compared to conventionalposterior stabilized or posterior cruciate retaining total kneearthroplasty procedures.

Properly controlling and managing the abovementioned degrees of freedomand other factors during surgery is one of the keys to a clinically andcommercially successful bicruciate retaining arthroplasty. Clinicalsuccess often depends on the ability of a surgeon to accurately andproperly implant a well-designed prosthesis in order to achieve theadvantages provided by the well-designed prosthesis. Commercial successoften depends on the ability of the surgeon to accurately and properlyimplant a well-designed prosthesis with confidence, reproducibility andspeed. Some, although not necessarily all, of the embodiments describedherein address these concerns.

Of all knee arthroplasty procedures, the risks associated with tibialresection degrees of freedom (i.e., varus/valgus angle, posterior slopeangle, and resection depth) are greater for bicruciate-retainingarthroplasty procedures than for posterior-stabilized or posteriorcruciate-retaining procedures. This is because varus/valgus angle,posterior slope angle, and resection depth directly affect the operationof the cruciates in guiding proprioceptive joint motion. Moreover, therisks associated with the additional degrees of freedom specific tobicruciate retaining arthroplasty (particularly internal/externalrotation angle and medial/lateral position of the tibial plateau andeminence resections) can include severe penalties for error, includingbut not limited to compromised structural integrity of the tibialeminence, compromised joint motion, and/or compromised cortical rimcoverage. Errors associated with any of the five degrees of freedomassociated with a bicruciate retaining procedure may present a surgeonwith complex judgment decisions (i.e., to favor achieving the bestpossible cortical coverage over providing maximum preservation of thetibial eminence and its anterior and posterior cruciate ligamentattachment sites). Such judgment decisions may include, for instance,whether or not to re-cut a bone to correct a perceived error, or tosimply let the error remain. Re-cutting decisions contribute to anincrease in both time and complexity, and may subsequently increase thelikelihood of propagating further errors.

Embodiments of the bicruciate retaining total knee arthroplastytechniques and instrumentation described herein present surgeons with atruly complex surgery in a simplified format through thoughtfulorganization, reduction, and readily accessible information. As will bediscussed herein, these embodiments may provide, at least in part,improved devices and methods for preparing a proximal tibia during totalknee arthroplasty procedures. The devices and methodologies describedbelow can be generally divided into three stages including: controllingdegrees of freedom, making resections, and performing finishing steps.

As will be discussed in greater detail below, controlling degrees offreedom can include one or more of the steps of: roughly setting tibialresection depth, setting a neutral (or reference) varus/valgus angle forthe medial and lateral tibial plateau resections, setting a neutral (orreference) posterior slope for the medial and lateral tibial plateauresections, fine-tuning the posterior slope angle and/or varus/valgusangle for the medial and lateral tibial plateau resections, settingmedial-lateral positioning of the medial and lateral eminence bone cuts,setting an internal-external rotation angle for the medial and lateraleminence bone cuts (if desirable), determining an appropriately-sizedtibial eminence width (related to implant size), and fine tuning thedepth for both the medial and lateral tibial plateau resections. As willalso be discussed in greater detail below, making resections cangenerally include one or more of the steps of making a medial tibialplateau resection, making medial and lateral tibial eminence bone cuts,performing a medial plateau balance check, performing a lateral tibialplateau resection, assessing fit of the implant to bone, and performinga trial reduction to assess range of motion, joint stability, and softtissue tension. Additionally, finishing steps can generally include oneor more of the steps of making an anterior eminence bone cut and ananterior tibial plateau resection to remove an anterior block portion ofthe tibial eminence, removing bone at eminence corners, assessing fit ofthe implant to bone, punching one or more keel cavities or openings intothe cancellous bone of the proximal tibia, and implanting a tibialcomponent. Various devices and instruments for performing these stepsand procedures will now be discussed in detail below.

A. Datum Block

Referring to FIG. 5, show therein is a datum or alignment block 100according to one form of the present invention, as shown in relation tothe proximal tibia 12. The datum block 100 can be used as a fundamentalinstrument to provide a neutral/reference tibial foundation to whichother devices or instruments may be engaged to and referenced from. Thedatum block 100 generally includes a main body 102 configured forattachment to the proximal tibia 12, a reference bench or table 104extending from the main body 102 and configured for removable attachmentof various devices/instruments to the datum block 100, and a locking orpinch force mechanism 106 associated with the main body 102 andconfigured to removably lock other devices/instruments to the datumblock 100.

As shown in FIG. 5, in the illustrated embodiment, the datum block 100is configured to engage and support an extramedullary alignment rod or“up rod” 108 having a central longitudinal axis L. In one embodiment,one end of the alignment rod 108 is removably attached to the main body102 of the datum block 100. However, other embodiments are alsocontemplated wherein an end of the alignment rod 108 is removably orpermanently attached to the main body 102 or other portions of the datumblock 100. In still other embodiments, the opposite end of the alignmentrod 108 may be removably attached to a mounting device associated withthe patient's ankle to provide additional support and alignmentcapabilities. As should be appreciated, the alignment rod 108 may bealigned with axes and/or other features associated with the proximaltibia 12 to correspondingly align the datum block 100 (and other devicesand instruments attached to the datum block 100) with such axes/featuresand/or other anatomic structures. For example, in some cases it may bedesirable to roughly align the central longitudinal axis L of thealignment rod 108 along the anatomic and/or mechanical axis 13 of thetibia (in one or both of the sagittal and coronal planes) at thetubercle of the proximal tibia 12, while offsetting the datum block 100from the tubercle of the proximal tibia 12. Other alignment techniquesand procedures are also contemplated as falling within the scope of thepresent invention, many of which would occur to one having ordinaryskill in the art. In the illustrated embodiment, the alignment rod 108has a non-circular transverse cross section, and more specifically hasat least one flat section for constraining rotation. However, in otherembodiments, the alignment rod 108 may be provided with other suitableshapes and configurations, including a circular transverse crosssection.

Referring collectively to FIGS. 6A-6F in combination with FIG. 5, showntherein are further details associated with the datum block 100. In theillustrated embodiment, the main body 102 of the datum block 100includes a superior portion 110 and an inferior portion 130. In oneembodiment, the superior and inferior portions 110, 130 are formedunitarily with one another to define a single-piece monolithicstructure. However, in other embodiments, the superior and inferiorportions 110, 130 may be formed separately and coupled together todefine an integrated multi-piece structure.

In the illustrated embodiment, the superior portion 110 of the main body102 of the datum block 100 defines a substantially flat/planar superiorsurface 112, a groove or indicia 114 extending along the planar superiorsurface 112 in an anterior-posterior direction, and a cavity 116 (FIGS.5 and 6D) extending through the superior portion 110 from the planarsuperior surface 112 in a superior-inferior direction. In oneembodiment, the groove/indicia 114 is generally aligned with the centrallongitudinal axis L of the alignment rod 108 and provides a visualindication or marker that may be aligned with the center of the proximaltibia 12 (i.e., alignable with the center of the tibial eminence 14) toroughly locate the datum block 100 in the appropriate position andorientation relative to the proximal tibia 12. The superior portion 110of the main body 102 further defines an elongate pin-receiving slot 120extending therethrough in an anterior-posterior direction and having aslot length/extending generally in a superior-inferior direction and aslot width w extending in a medial-lateral direction. The superiorportion 110 also defines a plurality of pin-receiving openings 122extending therethrough generally in an anterior-posterior direction. Aswill be discussed in further detail below, the elongate slot 120 issized and configured for receipt of a provisional attachment pin orfastener 190 configured to provisionally attach the datum block 100 tothe proximal tibia 12, and the openings 122 are each sized andconfigured for receipt of a terminal attachment pin or fastener 196configured to terminally attach the datum block 100 to the proximaltibia 12.

In the illustrated embodiment, the inferior portion 130 of the main body102 of the datum block 100 defines a first passage 132 extendingpartially therethrough from an inferior surface in an inferior-superiordirection and having an inner cross section corresponding to the outercross section of the alignment rod 108 (FIG. 6D). The inferior portion130 of the main body 102 further defines a second passage 134 extendingpartially therethrough from an anterior end surface in ananterior-posterior direction and communicating with the first passage132 (FIGS. 5 and 6C). As illustrated in FIG. 6D, the first passage 132is sized and configured to receive an end portion of the alignment rod108 therein. As illustrated in FIG. 6C, the second passage 134 is atleast partially threaded and is configured for threaded engagement witha set screw or fastener 136 having an end portion that engages thealignment rod 108 to retain the alignment rod 108 within the firstpassage 132. As further illustrated in FIG. 6D, the inferior portion 130of the main body 102 also defines a visualization opening 138 positionedadjacent the first passage 132 and communicating with the second passage134 to provide access to the second passage 134 and visualization of theset screw 136. As also illustrated in FIG. 6D, the inferior portion 130of the main body 102 also defines an aperture 140 positioned adjacentthe anterior surface of the inferior portion 130 and sized andconfigured for receipt of a retention pin 142 that serves to prevent theset screw 136 from backing entirely out of the second passage 134. Asillustrated in FIG. 6B, a posteriorly-facing surface of the inferiorportion 130 of the main body 102 defines a radially contoured groove 144extending along a generally uniform radius relative to a central pivotaxis C and terminating at an end surface 146, the purpose of which willbe discussed below.

As indicated above, the datum block 100 includes a reference bench ortable 104 extending from the main body 102 and configured for removableattachment of various devices/instruments to the datum block 100. In theillustrated embodiment, the reference bench 104 is formed unitarily withthe superior portion 110 of the main body 102 to define a single-piecemonolithic structure. However, in other embodiments, the reference bench104 may be formed separately from the main body 102 and coupled to thesuperior portion 110 to define an integrated multi-piece structure. Asshown in FIG. 6B, in the illustrated embodiment, the reference bench 104has a non-rectangular trapezoidal-shaped configuration defining anarrowing or tapered width extending away from the main body 102 in amedial-lateral direction. However, other suitable shapes andconfigurations of the reference bench 104 are also contemplated asfalling within the scope of the present invention.

As shown in FIGS. 6A-6C, the reference bench 104 defines a substantiallyflat/planar superior surface 150 and a substantially flat/planarinferior surface 152, with the planar superior and inferior surfaces150, 152 preferably arranged generally parallel with one another,although non-parallel arrangements of the planar superior and inferiorsurfaces 150, 152 are also contemplated. Additionally, the planarinferior surface 152 of the reference bench 104 is positioned oppositethe planar superior surface 112 of the main body 102 to thereby define aspace or gap 154 therebetween (FIGS. 6A-6C) sized and configured forreceipt of plate-like portions of other devices and instruments to beconnected with the datum block 100, details of which will be set forthbelow. In the illustrated embodiment, the planar inferior surface 152 ofthe reference bench 104 is preferably arranged generally parallel withthe planar superior surface 112 of the main body 102, althoughnon-parallel arrangements of the opposing surfaces are alsocontemplated. In the illustrated embodiment, the reference bench 104also defines a groove or indicia 156 extending along the planar superiorsurface 150 in an anterior-posterior direction. The groove/indicia 156is preferably arranged generally parallel with the groove/indicia 114extending along the planar superior surface 112 of the main body 102. Inone embodiment, the groove/indicia 156 provides a general visualindication or marker of the location of the vertical cut associated withthe medial resection of the proximal tibia 12.

As indicated above, the datum block 100 includes a locking or pinchforce mechanism 106 associated with the main body 102 that is configuredto removably lock various devices/instruments to the datum block 100.Referring to FIGS. 7A and 7B, illustrated therein are unlocked andlocked configurations of the datum block 100, respectively.Additionally, referring to FIGS. 8A and 8B, illustrated therein arecorresponding unlocked and locked configurations of the lockingmechanism 106, respectively.

In the illustrated embodiment, the locking mechanism 106 generallyincludes a lever arm or actuator member 160 pivotally attached to theinferior portion 130 of the datum block 100, and a gripper or actuatedmember 180 positioned within the cavity 116 in the superior portion 110of the datum block 100 and movably engaged with a proximal end portionof the lever arm 160. As will be discussed in further detail below,pivotal movement of the lever arm 160 in the direction of arrow Pcorrespondingly displaces the gripper member 180 in an inferior-superiordirection in the direction of arrow A to correspondingly compress thegripper member 180 against a plate-like portion of a device/instrumentpositioned within the space or gap 154 defined between the planarinferior surface 152 of the reference bench 104 and the planar superiorsurface 112 of the main body 102 of the datum block 100 to therebycapture the plate-like portion within the space 154 and retain thedevice/instrument in a fixed position and orientation relative to thedatum block 100. The locking or pinch force mechanism 106 thereby servesto maintain the position and angular alignment/orientation of variousdevices/instruments with respect to the datum block 100.

In the illustrated embodiment of the locking or pinch force mechanism106, the lever arm 160 has a generally rectangular bar-likeconfiguration that generally includes an inferior portion 162 and asuperior portion 164 that are connected to one another via a flexiblehinge portion 163 which permits the superior portion 164 to be displacedtoward/away from the inferior portion 162 to correspondingly vary a gapG between the inferior and superior portions 162, 164. The inferiorportion 162 of the lever arm 160 is pivotally attached to the inferiorportion 130 of the datum block 100 via a pivot pin 166 to thereby allowfor pivotal movement of the lever arm 160 relative to the datum block100 about a central pivot axis C. The inferior portion 162 of the leverarm 160 is also provided with a stop member or pin 167 posteriorlyoffset from the pivot pin 166 and configured to limit pivotal movementof the lever arm 160 away from the main body 102 of the datum block 100.As the lever arm 160 is pivoted about the pivot pin 166 away from themain body 102, the stop member 167 is displaced along the radiallycontoured groove 144 defined by the posteriorly-facing surface of theinferior portion 130 of the main body 102 (FIG. 6B) until the stopmember 167 is engaged against the end surface 146 of the groove 144,thereby preventing further pivotal movement of the lever arm 160 awayfrom the main body 102. Additionally, the inferior portion 162 of thelever arm 160 defines a passage 168 (FIG. 6D) anteriorly offset from thepivot pin 166 and extending through the inferior portion 162 in aninferior-superior direction. The passage 168 is at least partiallythreaded and is configured for threading engagement with an adjustmentbolt 170 having a threaded shank portion 170 a and a proximal end 170 bdefining a series of radially-extending notches or splined grooves 171.The inferior portion 162 of the lever arm 160 further includes aretaining pin 172 that at least partially extends into the passage 168to prevent the adjustment bolt 170 from backing entirely out of thepassage 168.

The superior portion 164 of the lever arm 160 includes a proximal endportion having a cam structure 174 that defines a superior cam surface176 that extends along an asymmetrical curve or contour relative to thecentral pivot axis C. The superior portion 164 further defines a splineor V-shaped projection 178 extending from an inferior surface thereofthat is sized and configured for engagement within one of theradially-extending notches or splined grooves 171 defined by theproximal end 170 b of the adjustment bolt 170. As should be appreciated,tightening the adjustment bolt 170 into the passage 168 in the lever arm160 forces the superior portion 164 of the lever arm 160 away from theinferior portion 162 to widen the gap G therebetween, which in turndisplaces the superior cam surface 176 of the cam structure 174 awayfrom the central pivot axis C. Additionally, engagement of the spline orV-shaped projection 178 of the lever arm 160 within one of theradially-extending notches or splined grooves 171 defined by theproximal end of the adjustment bolt 170 prevents the adjustment bolt 170from loosening and backing out of the passage 168 in the lever arm 160.

Referring to FIGS. 8A and 8B, in the illustrated embodiment of thelocking or pinch force mechanism 106, the gripper or actuated member 180is provided as a two-piece component including a superior component 182and an inferior component 186. In the illustrated embodiment, thesuperior component 182 is permitted to translate in an inferior-superiordirection generally along the arrow A, and the inferior component 186 isalso permitted to translate in an inferior-superior direction generallyalong the arrow A as well as in an anterior-posterior direction relativeto the superior component 182 generally along arrow B. The superiorcomponent 182 may be provided with a generally circular configurationsized for displacement within the cavity 116 in the main body 102 of thedatum block 100 generally along the arrow A. The superior component 182also defines a superior gripping surface 184 a that may be compressedagainst plate-like portions of devices/instruments positioned within thespace or gap 154 defined between the reference bench 104 and the mainbody 102 of the datum block 100, and further defines a substantiallyflat/planar inferior surface 184 b. The inferior component 186 may alsobe provided with a generally circular configuration sized fordisplacement within the cavity 116 in the main body 102 of the datumblock 100 in the inferior-superior direction generally along arrow A andin the anterior-posterior direction generally along the arrow B. Theinferior component 186 defines a substantially flat/planar superiorsurface 188 a configured for sliding engagement with the substantiallyflat/planar inferior surface 184 b of the superior component 182, andfurther defines an inferior bearing surface 188 b configured for slidingengagement with the superior cam surface 176 defined by the superiorportion 164 of the lever arm 160. In the illustrated embodiment, theinferior bearing surface 188 b defines a curved contour extending alonga generally uniform/constant radius. However, other suitable shapes andconfigurations of the inferior bearing surface 188 b are alsocontemplated.

As set forth above, FIGS. 7A/7B and FIGS. 8A/8B illustrate unlocked andlocked configurations of the datum block 100 and the locking or pinchforce mechanism 106. In the unlocked configuration, a plate-like portionof a device/instrument may be positioned within the space or gap 154defined between the planar inferior surface 152 of the reference bench104 and the planar superior surface 112 defined by the main body 102 ofthe datum block 100. The datum block 100 and the locking mechanism 106are then transitioned from the unlocked configuration illustrated inFIGS. 7A and 8A to the locked configuration illustrated in FIGS. 7B and8B by pivoting the lever arm 160 about the central pivot axis C in asuperior direction along arrow P. As should be appreciated, pivoting ofthe lever arm 160 along arrow P causes the superior cam surface 176defined by the superior portion 164 of the lever arm 160 to slidablyengage the inferior bearing surface 188 b defined by the inferiorcomponent 186 of the gripper member 180, which in turn displaces theinferior component 186 generally along arrow A as well generally alongarrow B. The inferior component 186 in turn forces the superiorcomponent 182 of the gripper member 180 in an inferior-superiordirection generally along arrow A and compresses the superior grippingsurface 184 a of the superior component 182 into compressed engagementagainst a plate-like portion of a device/instrument positioned withinthe space 154 defined between the reference bench 104 and the main body102 of the datum block 100 to thereby lock the device/instrument in aselect position and orientation relative to the datum block 100.

As should be appreciated, the compression or clamping force exerted bythe superior component 182 onto the plate-like portion of thedevice/instrument positioned within the space 154 may be adjusted orcalibrated to satisfy particular clamping/locking requirements.Specifically, the compression or clamping force may be adjusted viatightening or loosening of the adjustment bolt 170. For example,tightening of the adjustment bolt 170 forces the superior portion 164 ofthe lever arm 160 away from the inferior portion 162 to widen the gap Gtherebetween, which in turn displaces the superior cam surface 176 ofthe cam structure 174 away from the central pivot axis C to therebyincrease the compression or clamping force exerted by the superiorcomponent 182 of the gripper member 180 onto the plate-like portion ofthe device/instrument positioned within the space or gap 154 defined bythe datum block 100. Additionally, loosening of the adjustment bolt 170allows the superior portion 164 of the lever arm 160 to be displacedtoward the inferior portion 162 to reduce the gap G therebetween, whichin turn displaces the superior cam surface 176 of the cam structure 174toward from the central pivot axis C to thereby decrease the compressionor clamping force exerted by the superior component 182 of the grippermember 180 onto the plate-like portion of the device/instrumentpositioned within the space or gap 154 in the datum block 100.

As should be appreciated, the locking or pinch force mechanism 106 maybe transitioned from the unlocked configurations illustrated in FIGS. 7Aand 8A to the locked configurations illustrated in FIGS. 7B and 8B (andvice-versa) without the need for separate driver instruments or lockingtools (e.g., a hex driver or a wrench). Additionally, the clamping orcompression force exerted by the locking or pinch force mechanism 106may be easily adjusted via a single adjustment mechanism (i.e.,tightening or loosening of the adjustment bolt 170). Although aparticular type and configuration of the locking or pinch forcemechanism 106 has been illustrated and described herein for use inassociation with the datum block 100, it should be understood that othertypes and configurations of locking/pinching mechanisms or othercompression structures/devices are also contemplated for use inassociation with the present invention in addition to or in lieu of thelocking or pinch force mechanism 106.

Referring to FIG. 9, the datum block 100 is provisionally attached tothe proximal tibia 12 by a provisional attachment pin or fastener 190extending through the elongate slot 120 in the main body 102 of thedatum block 100. The provisional attachment pin 190 may include athreaded distal end portion (not shown) for anchoring in bone tissue,and a proximal head portion 192 having drive features that facilitatedriving of the provisional attachment pin 190 into tibial bone. In theillustrated embodiment, the drive features may include providing theproximal head portion 192 with a non-circular transverse cross sectionincluding, for example, one or more flattened regions. Additionally, theproximal head portion 192 may be provided with an enlarged annularregion or ring 194 having a transverse cross section sized larger thanthe slot width w of the elongate slot 120. The enlarged portion 194 ofthe head 192 thereby serves to retain the datum block 100 on theprovisional attachment pin 190 to prevent the datum block 100 frombecoming disengaged from the provisional attachment pin 190. However,because of the elongate slot 120, the datum block 100 is permitted totranslate along the provisional attachment pin 190 in asuperior-inferior direction (i.e., to adjust resection depth), rotateabout the provisional attachment pin 190 in a medial-lateral direction(i.e., to adjust the varus-valgus angle), rotate about the provisionalattachment pin 190 in an anterior-posterior direction (i.e., to adjustthe posterior slope angle), and translate along the provisionalattachment pin 190 in an anterior-posterior direction (as limited byengagement of the enlarged head portion 194 against the anterior surfaceof the main body 102 of the datum block 100). As should be appreciated,placement of the provisional attachment pin 190 within the elongate slot120 in the main body 102 of the datum block 100 provides fine-tuningcapability as to adjustment of the particular position and orientationof the datum block 100 relative to the proximal tibia 12 prior toterminal/final attachment to the proximal tibia 12.

Referring to FIG. 10, once the datum block 100 is positioned in theappropriate superior/inferior position along the proximal tibia 12 andis rotated to the appropriate medial-lateral angle andanterior-posterior angle, the datum block 100 may be terminally attachedto the proximal tibia 12 by a pair of terminal attachment pins orfasteners 196 a, 196 b extending through respective ones of thepin-receiving openings 122 in the main body 102 of the datum block 100.The terminal attachment pins 196 a, 196 b may include a threaded distalend portion (not shown) for anchoring in bone tissue, and a proximalhead portion 198 having features that facilitate driving of the terminalattachment pins 196 a, 196 b into tibial bone. In the illustratedembodiment, the drive features include providing the proximal headportion 198 with a non-circular transverse cross section including, forexample, one or more flattened regions. As shown in FIG. 10, thepin-receiving openings 122 and the terminal attachment pins 196 a, 196 bare oriented at an oblique angle relative to the elongate slot 120 andthe provisional attachment pin 190. As a result, the datum block 100 isretained in position relative to the proximal tibia 12 without having totighten the enlarged region 104 of the proximal head portion 192 of theprovisional attachment pin 190 against the main body 102 of the datumblock 100 and/or without having to engage a further attachment pin tothe datum block 100 at an oblique angle relative to the terminalattachment pins 196 a, 196 b.

B. Depth Stylus

Referring to FIG. 11, shown therein is a depth stylus 200 according toone form of the present invention, as attached to the datum block 100 inrelation to the proximal tibia 12. As will be discussed in greaterdetail below, the depth stylus 200 can be used as a multi-functionalmeasurement instrument to take pre-resection measurements andpost-resection measurements to verify and confirm the proper depth ofthe medial and lateral plateau resection cuts.

The depth stylus 200 generally includes a base portion or mounting block202 configured for attachment to the datum block 100, an articulatingpointer or stylus rod 204 configured to articulate relative to themounting block 202 and to engage a superior surface of the proximaltibia 12 for measurement relative to a reference plane, and an actuationor adjustment mechanism 206 engaged with the mounting block 202 and thestylus rod 204 to move the stylus rod 204 toward and away from themounting block 202 in an inferior-superior direction to correspondinglyadjust the vertical position of the stylus rod 204 relative to thereference plane, or vice-versa (i.e., to correspondingly adjust theposition of the reference plane relative to the stylus rod 204). Furtherelements and features associated with the components of the depth stylus200 will be set forth in greater detail below with particular referenceto FIGS. 12-14.

In the illustrated embodiment, the mounting block 202 is a single-piecemonolithic structure including a mounting portion 210 and a connectorportion 220. In one embodiment, the mounting portion 210 is divided intosuperior and inferior portions 212, 214, respectively, that areseparated from one another by a slot 216. The superior mounting portion212 has a plate-like configuration defining substantially flat/planarsuperior and inferior surfaces 217 a, 217 b, respectively. The inferiormounting portion 214 also has a plate-like configuration definingsubstantially flat/planar superior and inferior surfaces 218 a, 218 b,respectively. The slot 216 defined between the superior and inferiormounting portions 212, 214 has a slot width w that is sized for receiptof the reference bench 104 of the datum block 100 therein. Once thedepth stylus 200 is positioned in a desired position and orientationrelative to the reference bench 104 of the datum block 100, the lockingor pinch force mechanism 106 is actuated to lock the depth stylus 200 ina select position and orientation relative to the datum block 100.Actuation of the locking or pinch force mechanism 106 correspondinglycompresses the planar superior surface 218 a of the plate-like mountingportion 214 against the planar inferior surface 152 of the referencebench 104 to thereby capture/lock the plate-like mounting portion 214within the space 154 defined between the main body 102 and the referencebench 104 of the datum block 100, which in turn retains the depth stylus200 in a fixed position relative to the datum block 100. As should beappreciated, locking of the depth stylus 200 in a fixedinferior-superior position relative to the datum block 100 stabilizesthe depth stylus 200 during measurements, which in turn removes anelement of toggle/tolerance between the depth stylus 200 and the datumblock 100 to thereby improve the accuracy of the measurements taken withthe depth stylus 200.

In one embodiment, the connector portion 220 of the mounting block 202serves to interconnect the stylus rod 204 with the adjustment mechanism206. Specifically, the connector portion 220 defines a first passage 222extending laterally therethrough, and a second passage 224 extendingtherethrough in a superior-inferior direction and arranged generallyperpendicular to the first passage 222. Although the axial centerlinesof the first and second passages 222, 224 are offset from one another,the passages 222, 224 are positioned in communication with one another.As will be discussed below, the passages 222, 224 are sized andconfigured to house components of the stylus rod 204 and the adjustmentmechanism 206. The connector portion 220 further defines a third passage226 extending therethrough in a direction generally parallel with thesecond passage 224 and intersecting the first transverse passage 222.The third passage 226 provides visualization of and/or access tointernal components housed within the connector portion 220 of themounting block 202. As shown in FIGS. 11 and 13D, an anterior surface ofthe connector portion 220 defines a reference or measurement marker 228,the purpose of which will be discussed below.

In the illustrated embodiment, the stylus rod 204 generally includes amounting base portion 230 and a rod portion 240, each extendinggenerally along a longitudinal axis L. In one embodiment, the baseportion 230 has a generally rectangular bar-like configuration anddefines an axial opening (not shown) extending therethrough generallyalong the longitudinal axis L for receipt of the rod portion 240. Thebase portion 230 also defines a spacer or stem 232 extendingtransversely therefrom which is sized and configured for slidablereceipt within the superior-inferior passage 224 in the connectorportion 220 of the mounting block 202. As shown in FIGS. 13A and 13B, areference pin or marker 234 extends from an inferior surface of the baseportion 230 in a superior-inferior direction and is positioned adjacentthe distal end of the base portion 230. Additionally, the base portion230 further defines a series of opening or slots 236 extendingtherethrough in a superior-inferior direction.

In the illustrated embodiment, the rod portion 240 of the stylus rod 204generally includes an elongate rod portion 242, a handle or grip portion244 attached to the proximal end of the elongate rod portion 242, and apointer or reference bar 246 extending from a distal end of the elongaterod portion 242. In the illustrated embodiment, the elongate rod portion242 and the proximal handle portion 244 each have a generally circularouter cross section, and one side of the elongate rod portion 242 isprovided with a flattened or truncated surface 243 which serves tostabilize the rotational position of the elongate rod portion 242relative to the mounting base portion 230. However, it should beunderstood that other shapes and configurations of the elongate rodportion 242 and the proximal handle portion 244 are also contemplated.In one embodiment, the distal pointer 246 extends from the elongate rodportion 242 at an angle θ relative to the longitudinal axis L. In onespecific embodiment, the angle θ is approximately 35°. However, otherangles θ are also contemplated. Additionally, the thickness of thedistal pointer 246 inwardly tapers along its length to a reduced crosssection adjacent its distal end to thereby define a relatively pointeddistal end surface 248 to improve the accuracy of the depth stylus 200.

Referring to FIG. 14, shown therein is one embodiment of the adjustmentmechanism 206 which, as indicated above, serves to displace the stylusrod 204 toward and away from the mounting block 202 in aninferior-superior direction to correspondingly adjust the position ofthe stylus rod 204 relative to a reference plane, or vice-versa. In theillustrated embodiment, the adjustment mechanism 206 generally includesa rotational actuator or drive member 250 and a linear actuator orplunger member 270. The rotational actuator 250 includes a thumb wheelor knob grip 252, a stem or shaft 254 extending axially from the thumbwheel 252 and arranged along a rotational axis R, and a pinion gear 256coupled to the shaft 254 and defining a series of gear teeth 258. Thethumb wheel 252 includes a number of scalloped or recessed regions 260that facilitate manual rotation of the thumb wheel 252 about therotational axis R by a user. The thumb wheel 252 also includes numeralsor other indicia/markings 262 positioned uniformly about an outercircumferential surface of the thumb wheel 252, the purpose of whichwill be discussed below. As should be appreciated, the shaft 254 isrotationally mounted within the transverse passage 222 extending throughthe connector portion 220 of the mounting block 202 to allow rotationalmovement of the shaft 254 and the pinion gear 256 about the rotationalaxis R upon exertion of a rotational force or torque onto the thumbwheel 252. The thumb wheel 252 may also be provided with one or moreprojections or detents 264 extending laterally from an inner sidesurface of the thumb wheel 252 which are positionable within recesses orgrooves (not shown) formed in an adjacent side surface of the mountingblock 202 to provide a certain degree of resistance to rotationalmovement of the drive member 250 to allow incremental rotationalmovement of the drive member 250 relative to the mounting block 202.

In the illustrated embodiment, the plunger member 270 of the adjustmentmechanism 206 includes an actuated shaft or rack 272 extending generallyalong a displacement axis D and defining a series of notches or gearteeth 274 positioned along its length. The plunger member 270 furtherdefines an enlarged head or guiding portion 276 positioned adjacent aninferior end of the rack 272 which is sized and configured for slidabledisplacement within the inferior portion of the passage 224 in theconnector portion 220 of the mounting block 202. In one embodiment, theenlarged head 276 has a generally circular outer cross sectioncorresponding to the circular inner cross section of the inferiorportion of the passage 224, and also defines a series of scallops orrecesses 278 formed along the outer circumferential surface of theenlarged head 276 to promote sliding engagement of the enlarged head 276along the inferior portion of the passage 224. As should be appreciated,exertion of a rotational force or torque onto the thumb wheel 252rotates the shaft 254 and the pinion gear 256 about the rotational axisR, which in turn intermeshes the gear teeth 258 of the pinion gear 256with the notches/teeth 274 on the rack 272 to correspondingly displacethe plunger member 270 along a displacement axis D, which therebyresults in displacement of the stylus rod 204 toward and away from themounting block 202 (or vice-versa) to correspondingly adjust theinferior-superior position of the stylus rod 204 relative to a referenceplane.

Referring once again to FIG. 11, once the depth stylus 200 is locked inposition relative to the datum block 100, the stylus rod 204 can berotationally displaced relative to the mounting block 202 about thedisplacement axis D, and the rod portion 240 of the stylus rod 204 canbe axially displaced along the longitudinal axis L relative to the baseportion 230 to correspondingly position the distal end surface 248 ofthe pointer 246 at an infinite number of positions along the outersurface of the proximal tibia 12. Additionally, the inferior-superiorposition of the stylus rod 204 along the displacement axis D can also beadjusted relative to the mounting block 202 by turning the thumb wheel252 in a clock-wise or counter clock-wise direction. As should beappreciated, the position of the distal end surface 248 of the pointer246 can therefore be adjusted in three dimensions for positioning at anypoint along the outer surface of the proximal tibia 12.

Once the distal end surface 248 of the pointer 246 is positioned inabutment against a selected point P₁ along the outer surface of theproximal tibia 12 (e.g., along the medial tibial plateau 16 a), the usercan determine/measure the distance of the selected point P₁ relative toa reference plane in an inferior-superior direction. In one embodiment,the reference plane comprises the plane formed by the superior surface150 of the reference bench 104 of the datum block 100. However, itshould be understood that the depth stylus 200 may be configured todetermine/measure the distance of selected points along the proximaltibia 12 in an inferior-superior direction relative to other referenceplanes. As will be discussed in further detail below, the plane definedby the superior surface 150 of the reference bench 104 defines thecutting plane along which horizontal medial and lateral resection cutsC_(HM), C_(VM) (FIGS. 20B and 20C) will be formed during resection ofthe medial and lateral tibial plateau regions 16 a, 16 b. Additionally,as shown in FIG. 11 and as set forth above, the datum block 100 may beprovisionally attached to the proximal tibia 12 by the provisionalattachment pin 190 extending through the elongate slot 120 in the mainbody 102 of the datum block 100. Because the datum block 100 is not yetterminally attached to the proximal tibia 12 (i.e., is not securelyattached to the proximal tibia by the terminal attachment pins 196), thedatum block 100 is permitted to translate in a superior-inferiordirection via sliding engagement of the provisional attachment pin 190along the length of the elongate slot 120, which in turn correspondinglyadjusts the plane defined by the superior surface 150 of the referencebench 104 and the proposed/intended resection depth of the horizontalmedial and lateral resection cuts C_(HM), C_(VM).

As should be appreciated, with the distal end surface 248 of the pointer246 positioned in abutment against the selected point P₁ along the outersurface of the proximal tibia 12, the superior-inferior position of thedatum block 100 may be adjusted via rotating the thumb wheel 252 in aclockwise or counter-clockwise direction, which in turn adjusts thesuperior-inferior position of the reference/cutting plane defined by thereference bench 104 on the datum block 100 to a desired resection depth(i.e., to a desired position for subsequent formation of the horizontalmedial and lateral resection cuts C_(HM), C_(VM)). As shown in FIG. 11,the inferior-superior distance from the selected point P₁ in contactwith the distal end surface 248 of the pointer 246 relative to thereference/cutting plane (i.e., the proposed/intended resection depth) isdetermined by observing which of the reference numerals 262 on the thumbwheel 252 is aligned with the reference marker 228 on the anteriorsurface of the mounting block 202 (i.e., reference numeral “9” in theillustrated embodiment). As should be appreciated, further adjustment orfine-tuning of the position of the reference/cutting plane defined bythe datum block 100 (i.e., the proposed/intended resection depth) can bemade by incrementally turning the thumb wheel 252 until a desiredposition of the reference/cutting plane (i.e., the resection depth) isachieved. At this point, the superior-inferior position of the datumblock 100 (and the desired resection depth) may be fixed by driving oneor more of the terminal attachment pins 196 through correspondingpin-receiving openings 122 in the datum block 100.

In one embodiment, the distal end surface 248 of the pointer 246 mayinitially be positioned and held in abutment against the selected pointP₁ along the outer surface of the proximal tibia 12, followed byrotation of the thumb wheel 252 to correspondingly adjust thesuperior-inferior position of the datum block 100 and thereference/cutting plane defined by the reference bench 104 until adesired resection level has been achieved (as indicated by the referencenumerals 262 on the thumb wheel 252 aligned with the reference marker228 on the mounting block 202). However, in another embodiment, theresection depth may be initially set by aligning the appropriatereference numeral 262 on the thumb wheel 252 with the reference marker228, followed by adjustment of the superior-inferior position of thedatum block 100 until the distal end surface 248 of the pointer 246 ispositioned in abutment against the selected point P₁ along the outersurface of the proximal tibia 12.

In addition to using the depth stylus 200 to position the datum block100 at a desired superior-inferior position and the reference/cuttingplane at a desired resection depth, it should be understood that thedepth stylus 200 may be used at any time in a knee arthroplastyprocedure to measure and check/verify the superior/inferior position ofthe reference/cutting plane relative to any reference point on theproximal tibia 12 by positioning the distal end surface 248 of thepointer 246 in abutment against the reference point (i.e., viarotational/translational positional adjustment of the stylus rod 204 andinferior-superior positional adjustment via rotation of the thumb wheel252) and observing which of the reference numerals 262 on the thumbwheel 252 is aligned with the reference marker 228 on the mounting block202.

Referring to FIG. 15, shown therein is another operational position ofthe stylus rod 204 wherein the distal end surface 248 of the pointer 246is positioned in contact with another selected point P₂ along theproximal tibia 12 (e.g., along the lateral tibial plateau 16 b) todetermine the distance of the selected point P₂ from the reference planein an inferior-superior direction. Once again, the inferior-superiordistance of the selected point P₂ in contact with the distal end surface248 of the pointer 246 relative to the reference plane (i.e., the planeformed by the superior surface 150 of the reference bench 104 of thedatum block 100) may be determined by observing which of the referencenumerals 262 is aligned with the reference marker 228 (i.e., referencenumeral “12” in the illustrated embodiment).

Referring now to FIGS. 16A and 16B, shown therein is an alternativeoperational configuration of the depth stylus 200. In this alternativeoperational configuration, the depth stylus 200 may be removed/detachedfrom the datum block 100 (via de-actuation of the pinch force mechanism106) and used as a hand-held caliper-type instrument. This alternativeoperational configuration of the depth stylus 200 may be particularlyuseful, for example, in providing measurements of a resected bonefragment F removed/resected from proximal tibia 12. However, it shouldbe understood that in this alternative operational configuration, thedepth stylus 200 may be used to provide measurements of other structuresas well including, for example, attached bone portions of the distalfemur 10 or the proximal tibia 12 (i.e., the tibial eminence followingresection), femoral or tibial bone implant components, or otherstructures of devices that require measurement.

As shown in FIG. 16A, in the alternative operational configuration ofthe depth stylus 200, the rod portion 240 of the stylus rod 204 may beretracted into the base portion 130 and rotated 180° about thelongitudinal axis L relative to the base portion 230 to position thedistal pointer 246 in a refracted position and in an upwardly extendingorientation to avoid interference with the bone fragment F (or anotherstructure or device) being measured. The bone fragment F may be insertedinto the open space between the planar superior surface 217 a of themounting block 202 and the reference pin 234, with the reference pin 234positioned directly above a selected point P₃ along the bone fragment Fto be measured. As shown in FIG. 16B, the inferior-superior position ofthe stylus rod 204 may then be adjusted relative to the mounting block202 along the displacement axis D by turning the thumb wheel 252 untilthe distal end surface of the reference pin 234 is positioned in contactwith the selected point P₃ along the bone fragment F, and the oppositesurface of the bone fragment F (i.e., the planar surface of the bonefragment F) is slightly compressed into contact with the planar superiorsurface 217 a of the mounting block 202. The measured distance betweenthe selected point P₃ and the opposite surface of the bone fragment F(i.e., the thickness of the bone fragment F) is determined by observingwhich of the reference numerals 262 on the thumb wheel 252 is alignedwith the reference marker 228 on the anterior surface of the mountingblock 202 (i.e., reference numeral “9” in the illustrated embodiment).

C. Eminence Stylus

Referring to FIG. 17A, shown therein is an eminence stylus 300 accordingto one form of the present invention, as attached to the datum block 100in relation to the proximal tibia 12. As will be discussed in greaterdetail below, the eminence stylus 300 includes alignment features thatserve to align the eminence stylus 300 relative to anatomic features ofthe proximal tibia 12 and/or the distal femur 10, and also includesguide or capture features that serve to guide an oscillating orreciprocating saw or another type of cutting instrument along variouscutting planes to form multiple resection cuts in the proximal tibia 12.

The eminence stylus 300 generally includes a base portion or body 302configured for attachment to the datum block 100, a carriage 304 movablyattached to the base portion 302 and configured for linear displacementalong a longitudinal displacement axis L arranged in a generallyanterior-posterior direction, and a pair of articulating arms orindicator members 306 a, 306 b pivotally attached to the carriage 304and configured for pivotal displacement about a pivot axis P arrangedgenerally perpendicular to the longitudinal displacement axis L. Furtherelements and features associated with the eminence stylus 300 will beset forth in greater detail below.

Referring to FIG. 17B, shown therein is an eminence stylus 300 aaccording to another form of the present invention, as attached to theproximal tibia 12. In many respects, the eminence stylus 300 a isconfigured similar to the eminence stylus 300 illustrated and describedabove. However, the eminence stylus 300 a includes other elements,features and operational characteristics not found in the eminencestylus 300, the details of which will be described below.

It should be understood that like elements and features associated withthe eminence stylus 300 and the eminence stylus 300 a are referred tousing the same reference numbers. Similar to the eminence stylus 300,the eminence stylus 300 a generally includes a base portion or body 302,a carriage 304 movably attached to the base portion 302 and configuredfor linear displacement along a longitudinal displacement axis Larranged in a generally anterior-posterior direction, and a pair ofarticulating arms or indicator members 306 a, 306 b pivotally attachedto the carriage 304 and configured for pivotal displacement about apivot axis P arranged generally perpendicular to the longitudinaldisplacement axis L and the anatomic axis 13 of the tibia. Furtherdetails associated with the elements and features of the base portion302, the carriage 304 and the indicator members 306 a, 306 b of theeminence stylus 300 a need not be discussed herein, it being understoodthat these elements and features may be configured identical to likecomponents of the eminence stylus 300. However, in other embodiments,the base portion 302, the carriage 304 and/or the indicator members 306a, 306 b of the eminence stylus 300 a may be configured different fromthose of the eminence stylus 300. Unlike the eminence stylus 300 whichis configured for releasable attachment to the datum block 100 or asimilar instrument or device, the eminence stylus 300 a is configuredfor attachment directly to the proximal tibia 12. Specifically, in theillustrated embodiment, the eminence stylus 300 a includes a mountingblock 380 defining at least one pin-receiving opening 382 extendingtherethrough in an anterior-posterior direction, and with one or moreattachment pins 196 a, 196 b positioned within and extending through theopening 382 to operatively attach the eminence stylus 300 a to theproximal tibia 12. Further elements and features associated with theeminence stylus 300 a will be set forth in greater detail below.

Referring collectively to 18A-18F, in the illustrated embodiment of theeminence stylus 300 shown in FIG. 17A, the base portion 302 is asingle-piece monolithic structure and generally includes a base plate310, a pair of medial and lateral cutting guide flanges 312 a, 312 bextending from the base plate 310 in an inferior-superior direction andspaced apart to define an open inner region or yoke therebetween, aninferior mounting flange 314 extending from the base plate 310 in amedial-lateral direction, and a superior cutting guide flange 316extending from the base plate 310 in a medial-lateral direction andsuperiorly offset from the inferior mounting flange 314 so as to definea slot 318 therebetween. Although the base portion 302 has beenillustrated and described as being formed as a single-piece monolithicstructure, in other embodiments, various pieces/elements of the baseportion 302 may be formed separately from one another and integratedinto a multi-piece assembly.

In one embodiment, the base plate 310 has a generally planarconfiguration and a generally rectangular shape. However, other shapesand configurations are also contemplated. The base plate 310 defines apair of circular pin receiving openings 320 a, 320 b extending entirelythrough the base plate 310 and aligned generally along the longitudinalaxis L in an anterior-posterior direction, and with the openings 320 a,320 b arranged symmetrical on opposite sides of the longitudinal axis L.Additionally, the base plate 310 includes a rectangular-shaped guidenotch or channel 322 (FIGS. 18C and 18F) formed in the superior surfaceof the base plate 310 and aligned generally along the longitudinal axisL in an anterior-posterior direction. The guide channel 322 is sized andconfigured to receive an inferior portion of the carriage 304 therein soas to aid in guidably displacing the carriage 304 linearly along thelongitudinal axis L (FIGS. 19A and 19B). The base plate 310 also definesa threaded aperture 324 (FIG. 18E) extending through the base plate 310in an inferior-superior direction and aligned generally with thelongitudinal axis L, and further defines a pair of threaded apertures326 a, 326 b extending at least partially through the base plate 310 inan inferior-superior direction and arranged symmetrically on oppositesides of the longitudinal axis L. The threaded apertures 326 a, 326 bare configured to threadingly receive a pair of fasteners or set screws328 a, 328 b.

As indicated above, the medial and lateral cutting guide flanges 312 a,312 b extend from the base plate 310 in an inferior-superior directionand are spaced apart to define an open inner region or yoketherebetween. In the illustrated embodiment, the medial and lateralcutting guide flanges 312 a, 312 b each have a triangular-shapedconfiguration. However, other shapes and configurations of the medialand lateral cutting guide flanges 312 a, 312 b are also contemplated.Additionally, the medial and lateral cutting guide flanges 312 a, 312 bdefine substantially flat/planar inner surfaces 330 a, 330 b,respectively, arranged generally parallel with one another and facingthe open inner region. The planar inner surfaces 330 a, 330 b arepreferably generally aligned with the central axes of the pin receivingopenings 320 a, 320 b, respectively. As will be discussed in furtherdetail below, the substantially flat/planar inner surfaces 330 a, 330 bof the medial and lateral cutting guide flanges 312 a, 312 b cooperatewith adjacent surfaces of the indicator members 306 a, 306 b to formmedial and lateral cutting guides or channels configured to guide anoscillating or reciprocating saw (or another type of cutting instrument)to form vertical cuts associated with the medial and lateral resectionof the proximal tibia 12.

As also indicated above, the inferior mounting flange 314 and thesuperior cutting guide flange 316 each extend from the base plate 310 ina medial-lateral direction and are offset from one another in aninferior-superior direction to define a slot 318 therebetween. In oneembodiment, the inferior mounting flange 314 has a generally rectangularconfiguration and the superior cutting guide flange 316 has a generallytrapezoidal-shaped configuration. However, other suitable shapes andconfigurations are also contemplated. In the illustrated embodiment, theinferior mounting flange 314 has a plate-like configuration definingsubstantially flat/planar superior and inferior surfaces 340, 342,respectively. Similarly, the superior cutting guide flange 316 likewisedefines substantially flat/planar superior and inferior surfaces 344,346, respectively. The slot 318 defined between the inferior mountingflange 314 and the superior cutting guide flange 316 has a slot width wthat is sized for receipt of the reference bench 104 of the datum block100 therein. As illustrated in FIG. 17A, once the eminence stylus 300 ispositioned in a desired position and orientation relative to thereference bench 104 of the datum block 100, the locking or pinch forcemechanism 106 of the datum block 100 is actuated to compress thesuperior surface 340 of the inferior mounting flange 314 against theinferior surface 152 of the reference bench 104 to thereby lock theeminence stylus 300 in a select position and orientation relative to thedatum block 100.

As will be set forth in detail below, the substantially flat/planarinferior surface 346 defined by the superior cutting guide flange 316 ofthe eminence stylus 300 forms a superior boundary of a cutting guide. Inone embodiment, the substantially flat/planar inferior surface 346 ispreferably generally aligned with the central axis of the pin receivingopening 320 a (FIG. 18C). As illustrated in FIG. 20A, the substantiallyflat/planar inferior surface 346 of the superior cutting guide flange316 is aligned substantially parallel with and offset from thesubstantially flat/planar superior surface 150 of the reference bench104 of the datum block 100 to thereby form a medial cutting guide orchannel 348 defined between the adjacent inferior and superior surfaces346, 150. In one embodiment, the planar superior surface 150 defined bythe reference bench 104 is aligned generally tangent with the diameterof the medial pin receiving opening 320 a. As should be appreciated, themedial cutting guide 348 preferably defines a channel width sized inrelatively close tolerance with the cutting blade thickness of anoscillating or reciprocating saw (or another cutting device) to form asmooth and accurate medial resection cut in the proximal tibia 12,further details of which will be set forth below.

In the illustrated embodiment, the carriage 304 has a generally U-shapedconfiguration including a base wall 350 defining a substantiallyflat/planar superior surface, and a pair of side walls 352 a, 352 bextending from the base wall 350 in an inferior-superior direction anddefining substantially flat/planar inner side surfaces and substantiallyflat/planar outer side surfaces. The carriage 304 may also be providedwith an end wall 354 to provide further structural support and rigidityto the carriage 304. Additionally, the carriage 304 may be provided witha pair of projections or detents 353 a, 353 b extending laterallyoutward from outer surfaces of the side walls 352 a, 352 b,respectively, the purpose of which will be discussed below. The carriage304 also defines an elongate slot 356 having a length extendinggenerally along the longitudinal axis L. The carriage 304 furtherincludes a pin or fastener 358 (FIGS. 18D and 18F) including a threadedshank portion 358 a and an enlarged head portion 358 b. The threadedshank portion 358 a extends through the elongate slot 356 and isthreaded into the threaded aperture 324 in the base plate 310 (FIG.18E). In one embodiment, the enlarged head portion 358 b has a generallycircular outer cross section that is positioned in relatively closetolerance and sliding engagement with the substantially flat/planarinner side surfaces of the side walls 352 a, 352 b of the carriage 304(FIGS. 18D and 18F). As should be appreciated, the fastener 358 servesto retain the carriage 304 on the base portion 302 to prevent unintendedor inadvertent removal of the carriage 304. However, as will bediscussed in greater detail below, the carriage 304 may be axiallydisplaced relative to the base portion 302 along the longitudinal axis Lto provide a degree of adjustability to the eminence stylus 300.Additionally, as shown in FIG. 18C, an inferior region of the base wall350 and/or the side walls 352 a, 352 b is recessed into the guidechannel 322 formed along the superior surface of the base plate 310 tofacilitate guiding displacement of the carriage 304 along thelongitudinal axis L.

In the illustrated embodiment, the articulating arms or indicatormembers 306 a, 306 b each include a mounting plate portion 360 and anelongate blade portion 362. As should be appreciated, the mounting plateportion 360 and the blade portion 362 of the indicator members 306 a,306 b cooperate to define substantially flat/planar outer side surface364 a, 364 b, respectively. As shown in FIGS. 18C and 18D, theflat/planar outer side surface 364 a, 364 b of the indicator members 306a, 306 b are aligned substantially parallel with and offset from therespective flat/planar inner side surfaces 330 a, 330 b of the medialand lateral cutting guide flanges 312 a, 312 b to thereby form a medialcutting guide or channel 366 a defined between the adjacent sidesurfaces 330 a, 364 a, and a lateral cutting guide or channel 366 bdefined between the adjacent side surfaces 330 b, 364 b. As should beappreciated, the medial and lateral cutting guides 366 a, 366 bpreferably define a channel width sized in relatively close tolerancewith the cutting blade thickness of an oscillating or reciprocating saw(or another cutting device) to form smooth and accurate resection cutsin the proximal tibia 12, further details of which will be set forthbelow.

The mounting plate portions 360 of the indicator members 306 a, 306 bare pivotally attached to the side walls 352 a, 352 b of the carriage304 via one or more pivot pins 370 (FIG. 19B) to allow for pivotalmovement of the indicator members 306 a, 306 b about the pivot axis Pfrom a substantially horizontal orientation (FIG. 19B) to asubstantially vertical orientation (FIG. 19C). The ends or heads of thepivot pins 370 are flush with or recessed slightly below the flat/planarouter side surface 364 a, 364 b of the indicator members 306 a, 306 b toprovide a substantially smooth and uninterrupted cutting guide surface.The inner surfaces of the mounting portions 360 of the indicator members306 a, 306 b each define a series of recesses or grooves 372 (18F and19C) that are sized to receive the detents 353 a, 353 b to therebyprovide a certain degree of resistance to pivotal movement of theindicator members 306 a, 306 b about the pivot axis P to allow forincremental pivotal movement of the indicator members 306 a, 306 brelative to the carriage 304. The indicator members 306 a, 306 b maytherefore be provisionally maintained in a select pivotal position viapositioning of the detents 353 a, 353 b in select ones of therecesses/grooves 366. In one embodiment, the portion of the mountingplate 360 positioned adjacent the pivot axis P has a somewhat greaterthickness compared to the elongate blade portion 362 to provide theindicator members 306 a, 306 b with greater rigidity and structuralintegrity. Additionally, each of the elongate blade portions 362preferably defines substantially flat/planar upper and lower edges 374a, 374 b and a rounded distal end surface 376.

Although a particular shape and configuration of the indicator members306 a, 306 b has been illustrated and described herein, it should beunderstood that other suitable shapes and configurations are alsocontemplated. Additionally, although the indicator members 306 a, 306 bhave been illustrated as pivoting simultaneously with one another aboutthe pivot axis P relative to the carriage 304, it should be understoodthat the indicator members 306 a, 306 b may pivot independent from oneanother about the pivot axis P (i.e., the indicator members 306 a, 306 bmay be positioned at different angular orientations relative to oneanother). Furthermore, in the illustrated embodiment of the eminencestylus 300, the indicator members 306 a, 306 b pivot about the pivotaxis P along travel planes that are substantially parallel to oneanother. However, in other embodiments, the eminence stylus 300 may beconfigured such that the indicator members 306 a, 306 b pivot about thepivot axis P along travel planes that are not parallel to one another(i.e., are arranged oblique to one another).

Referring now to FIGS. 19A-19E, the carriage 304 may be axiallydisplaced relative to the base portion 302 along the longitudinal axis Lbetween a first fully extended posterior-most position (FIGS. 19A and19D) and a second fully retracted anterior-most position (19B and 19E).The eminence stylus 300 is therefore capable of translating the carriage304 (and the indicator members 306 a, 306 b attached to the carriage304) toward and away from the proximal tibia 12 (or distal femur 10) inan anterior-posterior direction along the longitudinal axis L (FIG.17A). As should be appreciated, axial displacement of the carriage 304relative to the base portion 302 is limited by abutment of the threadedshank portion 358 a of the fastener 358 against the end surfaces of theelongate slot 356 (i.e., axial displacement of the carriage 304 islimited by the length of the elongate slot 356). Additionally, it shouldalso be appreciated that the ability to translate the carriage 304 (andthe indicator members 306 a, 306 b attached to the carriage 304) alongthe longitudinal axis L may more easily accommodate for different sizesof knees (e.g., varying sizes of the distal femur 10 and the proximaltibia 12). Furthermore, the ability to translate the carriage 304 alongthe longitudinal axis L to the fully retracted anterior-most position(FIGS. 19B and 19E) allows the indicator members 306 a, 306 b to clearthe distal femur 10 for pivotal displacement about the pivot axis P totheir vertical orientation (FIG. 19C) which may be used to checkalignment with the anterior region of the distal femur 10. As should befurther appreciated, sliding displacement of the enlarged head portion358 b along the inner guide surfaces of the side walls 352 a, 352 band/or sliding displacement of the inferior region of the base wall 350along the guide channel 322 formed in the base plate 310 facilitatesmooth and uninhibited guiding displacement of the carriage 304generally along the longitudinal axis L as the carriage 304 is movedaxially relative to the base portion 302.

Referring to FIGS. 20A-20C, some of the operational characteristicsassociated with the eminence stylus 300 according to embodiments of theinvention will now be discussed. The eminence stylus 300 is initiallyprovisionally attached to the datum block 100 by positioning theinferior mounting flange 314 of the eminence stylus 300 into the slot orchannel 154 defined between the reference bench 104 and the main body102 of the datum block 100. In this provisional attachment arrangement,the position and orientation of the eminence stylus 300 may be adjustedrelative to the datum block 100 and various anatomic features associatedwith the proximal tibia 12 and the distal femur 10. In some embodiments,the indicator members 306 a, 306 b may be used to provide visualindicators to aid in adjusting the eminence stylus 300 to the desiredposition and orientation. For example, the longitudinal axis L and thespace between the indicator members 306 a, 306 b might be centrallypositioned and generally aligned with the anatomic axis 13 of the tibia,and the central plane extending between the space between the indicatormembers 306 a, 306 b might be arranged generally coplanar with thecentral plane of the tibia 12. Other alignment techniques and proceduresused by those of skill in the art are generally known and need not bediscussed in detail herein.

As illustrated in FIG. 20A, after the eminence stylus 300 is positionedin a desired position and orientation relative to the proximal tibia 12,the locking or pinch force mechanism 106 of the datum block 100 isactuated to compress the superior surface 340 of the inferior mountingflange 314 against the inferior surface 152 of the reference bench 104to thereby lock the eminence stylus 300 in the selected position andorientation. However, as should be appreciated, if further adjustment tothe position/orientation of the eminence stylus 300 becomes necessary oris desired, the locking or pinch force mechanism 106 of the datum block100 can simply be deactuated/unlocked to provide further adjustmentopportunity (i.e., by pivoting the lever arm 160 of the lockingmechanism 106 in a downward direction).

Referring to FIG. 20B, once the eminence stylus 300 is locked inposition relative to the datum block 100, a graduated tibial pin 390according to one form of the invention is inserted into the medial pinreceiving opening 320 a in the eminence stylus 300 and anchored to theproximal tibia 12. A second graduated tibial pin 390 may likewise beinserted into the lateral pin receiving opening 320 b and anchored tothe proximal tibia 12. Further details regarding the graduated tibialpin 390 and a technique for installation/use of the graduated tibial pin390 according to one form of the invention will be set forth in detailbelow. As should be appreciated, the graduated tibial pin 390 providesfurther stabilization and support to the eminence stylus 300 to preventunintended/unintentional movement of the eminence stylus 300 relative tothe proximal tibia 12 (and the datum block 100) during formation of theresection cuts. Additionally, the graduated tibial pin 390 also servesas a guard or stop during formation of the tibial resection cuts tocontrol the depth of the cuts and to prevent overcutting or notchingwhich might otherwise compromise the strength and integrity of thetibial eminence 14.

Once the graduated tibial pin 390 is inserted into the medial pinreceiving opening 320 a and anchored to the proximal tibia 12, anoscillating or reciprocating saw (or another cutting device) is insertedinto and displaced along the medial cutting guide 348 defined betweenthe inferior surface 346 of the superior cutting guide flange 316 (onthe eminence stylus 300) and the superior surface 150 of the referencebench 104 (on the datum block 100) to form a horizontal medial resectioncut C_(HM). As indicated above, the graduated tibial pin 390 serves as aguard or stop to control the depth of the horizontal resection cut andto prevent overcutting or notching of the tibial eminence 14. Afterformation of the horizontal medial resection cut C_(HM), the oscillatingor reciprocating saw (or another cutting device) is inserted into anddisplaced along the medial cutting guide 366 a defined between theadjacent flat/planar side surfaces defined by the medial cutting guideflange 312 a and the medial indicator member 306 a to form the verticalmedial resection cut C_(VM) to complete the medial resection of theproximal tibia 12. Once again, the graduated tibial pin 390 serves as aguard or stop to control the depth of the vertical resection cut and toprevent overcutting.

Following completion of the medial tibial resection, the graduatedtibial pin 390 can be removed from the medial pin receiving opening 320a and inserted into the lateral pin receiving opening 320 b of theeminence stylus 300 and anchored to the proximal tibia 12.Alternatively, a second graduated tibial pin (not shown) may be insertedinto the lateral pin receiving opening 320 b and anchored to theproximal tibia 12. The oscillating or reciprocating saw (or anothercutting device) is then inserted into and displaced along the medialcutting guide 366 b defined between the adjacent flat/planar sidesurfaces defined by the lateral cutting guide flange 312 b and thelateral indicator member 306 b to form a vertical lateral resection cutC_(VL) in the proximal tibia 12. Once again, the graduated tibial pin390 serves as a guard or stop to control the depth of the verticalresection cut and to prevent overcutting or notching. In one embodiment,a single-blade saw (or another type of cutting device) is used to formthe vertical medial resection cut C_(VM) and vertical lateral resectioncut C_(VL). However, in other embodiment, a dual-blade saw (or anothertype of cutting device) may be used to form the vertical medialresection cut C_(VM) and vertical lateral resection cut C_(VL)simultaneously. Examples of dual-blade saws suitable for use inassociation with the present invention are disclosed in U.S. patentapplication Ser. No. 12/790,137, the contents of which have beenincorporated herein by reference in their entirety.

It should be appreciated that while the medial and lateral cuttingguides 366 a, 366 b defined between the adjacent flat/planar sidesurfaces of the cutting guide flanges 312 a, 312 b and the mountingplate portions 360 of the medial and lateral indicator members 306 a,306 b serve as the primary guide structures (a complete saw bladecapture extending along both sides of the saw blade) for guiding the sawblade along a particular cutting plane (i.e., a vertical cutting plane),the elongate blade portions 362 of the indicator members 306 a, 306 balso serve as additional guide structures along regions of the proximaltibia 12 posterior to the cutting guides 366 a, 366 b during a cuttingoperation. In this manner, the elongate blade portions 362 of theindicator members 306 a, 306 b serve as an extension of the cuttingguides 366 a, 366 b to guide/control the tip and distal portion of thesaw blade and to control the path of the saw blade in locationsposterior to the cutting guides 366 a, 366 b, particularly when formingposterior portions of the vertical eminence resection cuts.Additionally, the elongate blade portions 362 of the indicator members306 a, 306 b also serve as positive inner boundaries or stops to protectthe bone intended for preservation (i.e., the unresected bone). Itshould also be appreciated that although the indicator members 306 a,306 b are illustrated and described as being positioned mesially orinwardly offset from the medial and lateral cutting guide flanges 312 a,312 b to form inner boundaries or stops to control/guide the position ofthe saw blade, in other embodiments, the indicator members 306 a, 306 bmay be positioned outward from the medial and lateral cutting guideflanges 312 a, 312 b to form outer boundaries or stops to control/guidethe position of the saw blade.

As shown in FIG. 20C, following the formation of the horizontal medialresection cut C_(HM), the vertical medial resection cut C_(VM), and thevertical lateral resection cut C_(VL), the eminence stylus 300 may beremoved from the datum block 100 to provide access to the mediallyresected tibia for inspection, trialing and/or measuring using the depthstylus 200 or other measuring instruments. If re-cutting of one or moreof the resection cuts is required or desired, the eminence stylus 300may be re-engaged with the datum block 100, re-positioned/re-alignedwith respect to the proximal tibia 12, and re-locked to the datum block100. Alternatively, other devices/instruments may be used to recut orperform other cutting operations on the proximal tibia 12, the detailsof which will be set forth below. As shown in FIG. 20C, due to thedesign and configuration of the datum block 100, one potential benefitor advantage provided by the present invention is that the planarsuperior surface 150 of the datum block 100 is arranged co-planar withthe horizontal medial resection cut C_(HM). Accordingly, the planarsuperior surface 150 of the datum block 100 and the horizontal medialresection cut C_(HM) extend along a single reference plane, which may bebeneficial when engaging other devices or instruments to the datum block100 and/or when performing other procedures or techniques on theproximal tibia 12.

Although the formation of the horizontal and vertical resection cuts onthe proximal tibia 12 have been illustrated and described as occurringin a particular order, it should be understood that other cuttingsequences are also contemplated. Additionally, although formation of thevertical lateral resection cuts C_(VL) has been illustrated anddescribed as occurring immediately after completion of the medial tibialresection, it should be understood that the eminence stylus 300 may beremoved from the datum block 100 after completion of the medial tibialresection to provide access to the medially resected tibia forinspection, trialing and/or measuring to verify the accuracy of themedial resection cuts (i.e., position, depth, posterior slope angle,varus/valgus angle, etc.). In this manner, if the medial resection isfound to be inaccurate and/or requires re-cutting, appropriatecorrections/adjustments can be made prior to forming the lateralresection cuts. The eminence stylus 300 (or other devices orinstruments) may be engaged with the datum block 100 andpositioned/aligned with respect to the proximal tibia 12 prior to beinglocked to the datum block 100, followed by re-cutting of the medialresections and/or formation of the vertical lateral resection cutsC_(VL).

Referring once again to FIG. 17B, shown therein is the eminence stylus300 a attached to the proximal tibia 12 by the attachment pins 196 a,196 b. In many respects, the eminence stylus 300 a is configured similarto the eminence stylus 300, generally including a base portion 302, acarriage 304 movably attached to the base portion 302 and configured forlinear displacement along the longitudinal displacement axis L, and apair of indicator members 306 a, 306 b pivotally attached to thecarriage 304 and configured for pivotal displacement about the pivotaxis P. However, unlike the eminence stylus 300 which is configured forindirect coupling to the proximal tibia 12 by way of the datum block100, the eminence stylus 300 a is configured for direct attachment tothe proximal tibia 12.

In the illustrated embodiment, the eminence stylus 300 a includes amounting block 380 defining at least one pin-receiving opening 382extending therethrough in an anterior-posterior direction, and with oneor more attachment pins 196 a, 196 b positioned within and extendingthrough the pin-receiving opening 382 and anchored to tibial bone tooperatively attach the eminence stylus 300 a to the proximal tibia 12.In one embodiment, the base portion 302 and the mounting block 380 areformed unitarily with one another to define a single-piece monolithicstructure. However, in other embodiments, the base portion 302 and themounting block 380 may be formed separately and coupled/interconnectedtogether to define an integrated multi-piece structure. In oneembodiment, the pin-receiving opening 382 is configured as an elongateslot having a slot length/extending generally in a medial-lateraldirection and including inferior and superior surfaces 382 a, 382 b thatare spaced apart to define a slot width w. The slot length/preferablyextends across substantially an entire width of the mounting block 380,and the slot width w is preferably sized in relatively close tolerancewith the outer diameter of the attachment pins 196 a, 196 b to providesecure and stable engagement between the mounting block 380 of theeminence stylus 300 a and the attachment pins 196 a, 196 b. Although thepin-receiving opening 382 is illustrated and described as an elongateslot, it should be understood that other configurations of thepin-receiving opening 382 are also contemplated including, for example,a circular configuration. Additionally, although both of the attachmentpins 196 a, 196 b are illustrated as extending through a singlepin-receiving openings 382, it should be understood that the mountingblock 380 may be provided with any number of the pin-receiving openings382, including two or more pin-receiving opening 382 sized andconfigured for individual receipt of respective ones of the attachmentpins 196 a, 196 b.

In the illustrated embodiment, the eminence stylus 300 a includes asuperior cutting guide flange 384 configured similar to the superiorcutting guide flange 316 of the eminence stylus 300. The superiorcutting guide flange 384 extends from the base portion 302 in amedial-lateral direction and is offset from a medial portion of themounting block 380 in an inferior-superior direction to thereby define acutting guide channel 386 therebetween. In one embodiment, the mountingblock 380 has a generally rectangular transverse cross-section and thesuperior cutting guide flange 384 has a generally trapezoidal-shapedtransverse cross-section. However, other suitable shapes andconfigurations are also contemplated. Additionally, in the illustratedembodiment, the mounting block 380 defines a substantially flat/planarsuperior surface 388 a and the superior cutting guide flange 384 definessubstantially flat/planar inferior surface 388 b, with the planarsuperior and inferior surfaces 388 a, 388 b offset from one another inan inferior-superior direction to define the cutting guide channel 386therebetween. The cutting guide channel 386 is sized for receipt of acutting device therein and is configured to guide the cutting devicegenerally along a cutting plane in a medial-lateral direction to form amedial resection cut in the proximal tibia 12. In this manner, themounting block 380 and the cutting guide flange 384 cooperate to definea cutting guide that is sized in relatively close tolerance with thethickness of the cutting device (e.g., a cutting blade of an oscillatingor reciprocating saw, or another type of cutting device) to form asmooth and accurate medial resection cut in the proximal tibia 12generally along the cutting plane of the cutting guide channel 386,further details of which have been set forth above with regard to theeminence stylus 300.

Having described the structural features associated with the eminencestylus 300 a, reference will now be made to attachment of the eminencestylus 300 a to the proximal tibia 12 according to one embodiment of thepresent invention. As discussed above in association with FIG. 10, oncethe datum block 100 is positioned in the appropriate superior/inferiorposition along the proximal tibia 12 and is rotated to the appropriatemedial-lateral angle and anterior-posterior angle, the datum block 100may be terminally attached to the proximal tibia 12 by a pair ofterminal attachment pins 196 a, 196 b extending through respective onesof the pin-receiving openings 122 in the main body 102 of the datumblock 100.

In some instances, it may be desirable to interchange the datum block100 with the eminence stylus 300 a or another instrument or device. Morespecifically, it may be desirable to remove the datum block 100 from theattachment pins 196 a, 196 b and replace the datum block 100 with theeminence stylus 300 a or other instruments or devices. Since theattachment pins 196 a, 196 b are preferably arranged generally parallelwith one another, the datum block 100 can be easily detached from theproximal tibia 12 by simply sliding the datum block 100 off of theattachment pins 196 a, 196 b in an anterior direction. Once the datumblock 100 is removed from the attachment pins 196 a, 196 b, the eminencestylus 300 a can be attached to the proximal tibia 12 using the sameattachment pins 196 a, 196 b previously used to attach the datum block100 to the proximal tibia 12 (FIG. 10). Specifically, the proximal endportions of the attachment pins 196 a, 196 b extending from the proximaltibia 12 may be inserted into the elongate slot 382 in the mountingblock 380, and the eminence stylus 300 a may be slid along the proximalend portions of the attachment pins 196 a, 196 b in ananterior-posterior direction and rotated about the pins 196 a, 196 b ina medial-lateral direction until the eminence stylus 300 a is properlypositioned and oriented relative to the proximal tibia 12. In oneembodiment, the eminence stylus 300 a is slid along the proximalportions of the attachment pins 196 a, 196 b in an anterior-posteriordirection until the eminence stylus 300 a abuts an anterior aspect ofthe proximal tibia 12.

As should be appreciated, since the eminence stylus 300 a is attached tothe proximal tibia 12 using the same attachment pins 196 a, 196 b thatwere used to attach the datum block 100 to the proximal tibia 12 (i.e.,the attachment pins 196 a, 196 b remain anchored to the proximal tibia12 after removal of the datum block 100), the position and orientationof the eminence stylus 300 a relative to the proximal tibia 12 isadvantageously based on the same points of reference used to set theposition and orientation of the datum block 100. Notably, removal of theattachment pins 196 a, 196 b from the proximal tibia 12 is not requiredto detach the datum block 100 from the proximal tibia 12 or to attachthe eminence stylus 300 a to the proximal tibia 12. Additionally, itshould be appreciated that the elongate pin-receiving slot 382 in themounting block 380 of the eminence stylus 300 a has the same relativeposition and orientation as corresponding pairs of the pin-receivingopenings 122 in the datum block 100. Therefore, the eminence stylus 300a may be interchanged with the datum block 100 using the same attachmentpins 196 a, 196 b previously used to attach the datum block 100 to theproximal tibia 12, and the eminence stylus 300 a may take on the sameposition and orientation relative to the proximal tibia 12 as the datumblock 100.

In one embodiment, the eminence stylus 300 a is arranged at a positionand orientation on the proximal tibia 12 that corresponds to the priorposition and orientation on the datum block 100. In one specificembodiment, the planar superior surface 388 a of the mounting block 380of the eminence stylus 300 a is arranged substantially parallel with thepreviously-positioned planar superior surface 150 of the reference bench104 of the datum block 100. In another specific embodiment, the planarsuperior surface 388 a of the eminence stylus 300 a is arrangedsubstantially co-planar with the previously-positioned planar superiorsurface 150 of the datum block 100. However, other embodiments are alsocontemplated wherein the planar superior surface 388 a of the eminencestylus 300 a may be arranged non-parallel with and/or non-coplanar withthe previously-positioned planar superior surface 150 of the datum block100. As should be appreciated, the attachment pins 196 a, 196 b providetwo reference points that define a datum plane or substantially planardatum joint that serves to attach the datum block 100 to the proximaltibia 12 in a select position and orientation corresponding to theprevious position and orientation of the datum block 100.

Additionally, in other embodiments of the invention, the eminence stylus300 a may include other structures/features that provide aneutral/reference tibial foundation to which other devices orinstruments may be engaged to and referenced from. For example, in someembodiments, the eminence stylus 300 a may be provided with a referencetable configured similar to the reference bench 104 illustrated anddescribed above with regard to the datum block 100 to provide astructure to which other instruments or devices may be lockinglyengaged. Additionally, in some embodiments, the eminence stylus 300 amay be provided with a lock mechanism similar to that of the lockingmechanism 106 of the datum block 100 to selectively and releasably lockother instruments or devices to a reference bench of the eminence stylus300 a.

Referring to FIGS. 21A and 21B, shown therein is an eminence stylus 300′according to another form of the present invention. Referring to FIG.22, shown therein is the eminence stylus 300′ attached to the datumblock 100 (which may in turn be anchored to the proximal tibia 12). Theeminence stylus 300′ is configured identical to the eminence stylus 300illustrated and described above with the exception of the additionalelements and features described below. Like the eminence stylus 300, theeminence stylus 300′ generally including a base portion or body 302′configured for attachment to the datum block 100, a carriage 304′movably attached to the base portion 302′ and configured for lineardisplacement along a longitudinal displacement axis L, and a pair ofarticulating arms or indicator members 306 a′, 306 b′ pivotally attachedto the carriage 304′ and configured for pivotal movement relative to thecarriage 304′. The elements and features associated with thesecomponents need not be discussed herein, it being understood that theelements and features associated with the base portion 302′, thecarriage 304′ and the indicator members 306 a′, 306 b′ are configuredidentical to like elements and features associated with the base portion302, the carriage 304 and the indicator members 306 a, 306 b of theeminence stylus 300.

Unlike the eminence stylus 300 which cooperates with the datum block 100to provide a single horizontal medial cutting guide 348 (as definedbetween the superior cutting guide flange 316 and the reference bench104), as illustrated in FIG. 22, the eminence stylus 300′ provides botha horizontal medial cutting guide 348′ and a horizontal lateral cuttingguide 380′. Specifically, like the horizontal medial cutting guide 348associated with the eminence stylus 300, the horizontal medial cuttingguide 348′ is likewise defined between the inferior surface 346′ of thesuperior cutting guide flange 316′ and the superior surface 150 of thereference bench 104 (FIG. 22). Additionally, the horizontal lateralcutting guide 380′ is defined between an inferior cutting guide flange382′ and a superior cutting guide flange 384′, each extending laterallyfrom the right hand side of the base plate 310′ in a medial-lateraldirection. In one embodiment, the inferior and superior cutting guideflanges 382′, 384′ are formed unitarily with the base plate 310′ so asto define a single-piece monolithic structure. However, in otherembodiments, one or both of the inferior and superior cutting guideflanges 382′, 384′ may be formed separately from the base plate 310′ andintegrated with the base plate 310′ to define a multi-piece assembly. Inthe illustrated embodiment, the inferior and superior cutting guideflanges 382′, 384′ each have an irregular shape. However, other suitableshapes and configurations are also contemplated including, for example,rectangular or trapezoidal shapes.

In the illustrated embodiment, the inferior cutting guide flange 382′defines a substantially flat/planar superior surface 386′, and thesuperior cutting guide flange 384′ similarly defines a substantiallyflat/planar inferior surface 388′. In one embodiment, the planarsuperior surface 386′ defined by the inferior cutting guide flange 382′is generally tangent with the diameter of the lateral pin receivingopening 320 b′, and is also arranged substantially co-planar with thesuperior surface 150′ defined by the reference bench 104 of the datumblock 100 (FIG. 22). The planar inferior surface 388′ of the superiorcutting guide flange 384′ is arranged substantially co-planar with theinferior surface 346 defined by the superior cutting guide flange 316′extending medially from the base plate 310′. Additionally, the planarsuperior surface 386′ of the inferior cutting guide flange 382′ isaligned substantially parallel with and offset from the planar inferiorsurface 388′ of the superior cutting guide flange 384′ to thereby formthe lateral cutting guide or channel 380′. As should be appreciated, thelateral cutting guide 380′ preferably defines a channel width equal tothe channel width of the medial cutting guide 348′, each being sized inrelatively close tolerance with the cutting blade thickness of anoscillating or reciprocating saw (or another cutting device) to formsmooth and accurate horizontal resection cuts in the proximal tibia 12.

As should be appreciated, the eminence stylus 300′ may be used in thesame manner as described above with regard to the eminence stylus 300 toform the horizontal medial resection cut C_(HM), the vertical medialresection cut C_(VM), and the vertical lateral resection cut C_(VL)(FIGS. 20A-20C). However, the eminence stylus 300′ may also be used toform a horizontal lateral resection cut C_(HL) (shown as a dashed linein FIG. 20C) to complete the lateral resection of the proximal tibia 12.Specifically, with the graduated tibial pin 390 inserted into thelateral pin receiving opening 320 b′ and anchored to the proximal tibia12, an oscillating or reciprocating saw (or another cutting device) maybe inserted into and displaced along the horizontal lateral cuttingguide 380′ defined between the inferior cutting guide flange 382′ andthe superior cutting guide flange 384′ to thereby form the horizontallateral resection cut C_(HL). As indicated above, the graduated tibialpin 390 serves as a guard or stop to control the depth of the horizontalresection cut and to prevent overcutting or notching of the tibialeminence 14 which might otherwise compromise the strength and integrityof the tibial eminence 14. After formation of the final resection cut,the eminences stylus 300′ may be removed from the datum block 100. Asshould be appreciated, the design of the eminence stylus 300′ allows forthe formation of all necessary resection cuts to complete medial andlateral resection of the proximal tibia 12.

D. Graduated Tibial Pin

Referring to FIG. 23, shown therein is a graduated tibial pin 390according to one form of the present invention for use in associationwith the eminence stylus 300 or the eminence stylus 300′. As indicatedabove, the graduated tibial pin 390 provides further stabilization andsupport to the eminence stylus 300, 300′ to preventunintended/unintentional movement of the eminence stylus 300 relative tothe proximal tibia 12 (and the datum block 100), and also serves as aguard or stop during formation of the tibial resection cuts to controlthe depth of the cuts and to prevent overcutting or notching which mightotherwise compromise the strength and integrity of the tibial eminence14. In the illustrated embodiment, the graduated tibial pin 390 isconfigured as an elongate rod extending along a longitudinal axis L andgenerally including a distal-most end 390 a, a distal boneengaging/anchoring portion 392, a proximal head portion 394, and amarked portion 396 including a series of markers or indicia 398positioned generally along the proximal region of the pin 390.

In one embodiment, the pin 390 has a substantially circular outer crosssection. However, other embodiments are also contemplated wherein thegraduated tibial pin 390 is provided with other cross-sectional shapes.In another embodiment, the distal bone engaging/anchoring portion 392includes a drill flute 392 a or another type of cutting feature toprovide the pin 390 with self-drilling/self-cutting capabilities, and athread cutting tap 392 b or another type of thread forming feature toprovide the pin 390 with self-tapping capabilities. The threads of thetap 392 b also serve to anchor the pin 390 in bone tissue to prevent thepin 390 from pulling out of the bone. However, it should be understoodthat in other embodiments, the pin 390 may be provided with other typesof anchor elements to retain the pin 390 in bone tissue, and need notnecessarily include self-drilling/self-cutting/self-cuttingcapabilities. In the illustrated embodiment, the proximal head portion394 is configured for coupling with a driver or another tool/instrumentcapable of exerting a rotational force or torque onto the pin 390 todrive the pin 390 into bone tissue. In one embodiment, the proximal headportion 394 is provided with one or more flattened or truncated regions394 a to facilitate the application of a rotational force or torque ontothe proximal head 394. However, other configurations are alsocontemplated including, for example, providing the proximal head 394with a hexagonal configuration for mating engagement with a hex-driver.In one embodiment, the series of markers or indicia 398 along the markedportion 396 comprise a series of bands or lines having varying widthsand/or a varying number of lines per band. However, other embodimentsare also contemplated wherein the markers or indicia 398 may comprisenumbers, letters, symbols, colors, or other readily identifiableindicia.

Referring now to FIGS. 24A-24C and 25A-25C, shown therein is thegraduated tibial pin 390 in relation to the proximal tibia 12 and theeminence stylus 300. As shown in FIGS. 24A and 25A, once the eminencestylus 300 is adjusted to a desired position and orientation relative tothe proximal tibia 12 and locked to the datum block 100, the graduatedtibial pin 390 is positioned atop the proximal tibia 12 and adjacent themedial flange 312 a of the eminence stylus 300, with the longitudinalaxis L of the pin 300 in general alignment with the indicator members306 a, 306 b and substantially perpendicular or normal to the mechanicalaxis 13 of the tibia. The anterior-posterior position of the graduatedtibial pin 390 is then adjusted until the distal-most end 390 a of thepin 390 is positioned slightly anterior to the posterior surface of theproximal tibia 12. The position of the distal-most end 390 a of the pin390 relative to the posterior surface of the proximal tibia 12 can bedetermined visually or manually by tactile touch. In thisposition/orientation of the pin 90, an observation/notation is made asto which of the markers or indicia 398 along the marked portion 396 ofthe pin 390 is aligned with a particular reference location, which inthe illustrated embodiment comprises the anterior end surface or edgedefined by the medial flange 312 a on the eminence stylus 300. However,other reference locations are also contemplated. As shown in FIGS. 24Aand 25A, the indicia 398 a is generally aligned with the anterior endsurface of the medial flange 312 a.

Referring to FIGS. 24B and 25B, the graduated tibial pin 390 is theninserted into the pin-receiving opening 320 a in the eminence stylus 300and is driven into the proximal tibia 12 until the noted indicia 398 ais generally aligned with the anterior end surface of the medial flange312 a. In this position, the graduated tibial pin 390 will be fullyengaged/anchored within the proximal tibia 12 with the distal-most end390 a of the pin positioned slightly anterior to the posterior surfaceof the proximal tibia 12. As should be appreciated, in this position,the graduated tibial pin 390 provides maximum protection againstovercutting of the horizontal and vertical resection cuts, particularlyalong the posterior region of the proximal tibia, the likes of whichmight otherwise result in weakening of the remaining portion of thetibial eminence 14 and/or tibial condyles and potential fracturing ofthe same. However, the above-discussed procedure for inserting thegraduated tibial pin 390 into the proximal tibia 12 ensures that thedistal-most end 390 a of the pin does not penetrate or puncture throughthe posterior surface of the proximal tibia 12, thereby avoidingpotential damage or trauma to soft tissue structures residing behind theposterior cortex which might otherwise be damaged by the distal-most end390 a of the pin 390 protruding through the posterior cortical wall.Accordingly, by controlling the insertion depth of the pin 390 into theproximal tibia 12, the position of the distal-most end 390 a of the pin390 relative to the posterior cortical wall can be correspondinglycontrolled, thereby minimizing the risks associated with over-insertionof the pin 30 (i.e., puncturing the posterior cortical wall andpotentially damaging adjacent soft tissue structures) andunder-insertion of the pin 30 (i.e., leaving the posterior region of theproximal tibia 12 unprotected against overcutting of the horizontal andvertical resection cuts and potentially compromising the structuralintegrity of the unresected bone via posterior tibial notching).

Referring to FIGS. 24C and 25C, illustrated therein is the proximaltibia 12 subsequent to formation of the horizontal and vertical medialresection cuts C_(HM), C_(VM) and removal of the medially resected bonefragment. As discussed above and as shown in FIGS. 24C and 25C, theabove-discussed procedure for inserting the graduated tibial pin 390into the proximal tibia 12 ensures that the distal-most end 390 a of thepin 390 is positioned proximately adjacent the posterior cortical wallW_(P) but does not penetrate or puncture through the posterior corticalwall W_(P), while at the same time providing maximum protection againstovercutting of the horizontal and vertical medial resection cuts C_(HM),C_(VM). Although the above-discussed procedure for controlling theinsertion depth of the graduated tibial pin 390 has been illustrated anddescribed in association with medial resection of the proximal tibia 12,it should be understood that the insertion procedure can likewise beused in association with lateral resection of the proximal tibia 12.

E. Lateral Cut Guide

Referring to FIG. 26, shown therein is a lateral cut guide 400 accordingto one form of the present invention, as attached to the datum block 100in relation to the proximal tibia 12. As should be appreciated, thelateral cut guide 400 is attached to the datum block 100 via the lockingor pinch force mechanism 106 of the datum block 100, details of whichhave been set forth above. Although the lateral cut guide 400 is shownattached to and used in association with the datum block 100, it shouldbe understood that the lateral cut guide 400 may also be attached to andused in association with the recut block 600 (discussed below) or otherdevices or instruments.

As will be discussed in greater detail below, the lateral cut guide 400includes guide or capture features that serve to guide an oscillating orreciprocating saw (or another type of cutting instrument) along acutting plane to form a horizontal lateral resection cut C_(HL) (FIG.29B) in the proximal tibia 12. As discussed above, the eminence stylus300 may be used to form a horizontal medial resection cut C_(HM), avertical medial resection cut C_(VM), and a vertical lateral resectioncut C_(VL) (FIGS. 26 and 29A). Upon removal of the eminence stylus 300from the datum block 100 and attachment of the lateral cut guide 400 tothe datum block 100, the lateral cut guide 400 may be used to form thehorizontal lateral resection cut C_(HL) (FIG. 29B) to complete thelateral resection of the proximal tibia 12. As also discussed above, theembodiment of the eminence stylus 300′ may alternatively be used to formeach of the resection cuts to perform complete medial and lateralresection of the proximal tibia 12 via a single instrument (the eminencestylus 300′) attached to the datum block 100.

Referring collectively to FIGS. 27, 28A and 28B, in the illustratedembodiment, the lateral cut guide 400 generally includes a medialmounting portion 402, a lateral guide portion 404, and a tibial pin 406attached to the mounting portion 402. In one embodiment, the mountingportion 402 and the guide portion 404 are formed unitarily with oneanother to define a single-piece monolithic structure. However, in otherembodiments, the mounting portion 402 and the guide portion 404 may beformed separately from one another and integrated together to form amulti-piece assembly. Additionally, in the illustrated embodiment, thetibial pin 406 is pivotally attached to the mounting portion 402 via apivot pin or hinge 408 to allow articulating pivotal movement of thetibia pin 406 relative to the mounting portion 402 about the pivot axisP (FIG. 28A). However, other embodiments are also contemplated whereinthe tibial pin 406 is fixedly attached to the mounting portion 402, orfixedly, pivotally and/or translatably attached to other portions of thelateral cut guide 400.

In one embodiment, medial mounting portion 402 has a plate-likeconfiguration and defines an elongate slot or channel 410 extendingtherethrough in an anterior-posterior direction to thereby define asuperior mounting plate portion 412 and an inferior mount plate portion414, each having a substantially flat/planar configuration and agenerally rectangular shape. The superior and inferior mounting plates412, 414 are connected to one another via a medial wall 416. Theinferior mounting plate 412 defines substantially flat/planar superiorand inferior surfaces 418, 420, respectively. Additionally, the superiormounting plate 414 may also define substantially flat/planar superiorand inferior surfaces. In one embodiment, the lateral guiding portion404 includes superior and inferior guide plate portions or wings 422,424 that extend from the superior and inferior mounting plates 412, 414,respectively. The superior guide plate 422 defines a substantiallyflat/planar inferior surface 426, and the inferior guide plate 422defines a substantially flat/planar superior surface 428. The planarinferior surface 426 of the superior guide plate 422 is alignedsubstantially parallel with and offset from the planar superior surface428 of the inferior guide plate 422 to thereby form a lateral cuttingguide or channel 430 defined between the adjacent inferior and superiorplanar surfaces 426, 428. As should be appreciated, the lateral cuttingguide channel 430 preferably defines a channel width sized in relativelyclose tolerance with the cutting blade thickness of an oscillating orreciprocating saw (or another cutting device) to form a smooth andaccurate horizontal lateral resection cut along the proximal tibia 12.The superior surface of the superior guide plate 422 and the inferiorsurface of the inferior guide plate 424 are tapered in a medial-lateraldirection to provide increased visualization of the proximal tibia 12during a cutting operation, but may alternatively be provided asflat/planar surfaces. Additionally, the lateral end portion of thecutting guide portion 404 preferably defines a concave region 405 thatmay serve as a soft tissue retractor to facilitate creation of space forentry of the sawblade into the lateral cutting guide channel 430 toavoid damage or trauma to the soft tissue.

The tibial pin 406 includes a base or mounting ring portion 440 (FIG.28B) configured for pivotal attachment to the mounting portion 402 (viapassing the pivot pin 408 through an opening in the mounting ring 440),and also includes an elongate pin portion 442 extending from themounting ring portion 440. Since the tibial pin 406 is positivelyconnected to the mounting portion 402, the risk of losing, misplacing ordropping the tibial pin 406 is removed. In one embodiment, the elongatepin portion 442 has a generally circular or square-shaped outer crosssection that is sized substantially equal to the outer cross section ofthe graduated tibial pin 390. As will be discussed below, the elongatepin portion 442 is positionable in the lateral pin opening O_(L) (FIG.29A) previously formed in the proximal tibia 12 by the graduated tibialpin 390 that was inserted into the lateral pin-receiving opening 320 bin the eminence stylus 300 and driven into the proximal tibia 12 priorto formation of the vertical lateral resection cut C_(VL) (FIG. 20C).The elongate pin portion 442 is also provided with a tapered distal end444 to facilitate insertion into the previously-formed lateral pinopening O_(L).

Referring collectively to FIGS. 26, 29A and 29B, shown therein is thelateral cut guide 400 attached to the datum block 100 in relation to theproximal tibia 12. Having described the structural features associatedwith the lateral cut guide 400, some of the operational characteristicsassociated with the lateral cut guide 400 according to variousembodiments of the present invention will now be discussed.

The lateral cut guide 400 is initially engaged to the datum block 100 byinserting the elongate pin portion 442 of the tibial pin 406 into thepreviously-formed lateral pin opening O_(L), and by positioning theinferior mounting plate 414 into the slot 154 defined between thereference bench 104 and the main body 102 of the datum block 100. Inthis initial engagement arrangement, since the tibial pin 406 ispivotally attached to the medial mounting portion 402 and since theelongate pin portion 42 is able to slide along the lateral pin openingO_(L), the position and orientation of the lateral cut guide 400 may beeasily adjusted relative to the datum block 100. Additionally, pivotalattachment of the tibial pin 406 to the mounting portion 402 allows thepin 406 to be adjustably maneuvered to conform to varying pin openingorientations and/or tibial bone shapes. However, it should be noted thatthe particular position and orientation of the lateral cut guide 400(other than the inferior-superior position) on the datum block is notcritical to the success/accuracy of the cutting operation. Additionally,as shown in FIGS. 29A and 29B, the shape/contour of the posterior regionof the lateral guiding portion 404 is preferably configured to abut theanterior outer surface of the proximal tibia 12 when the lateral cutguide 400 is engaged to the datum block 100 to provide additionalstabilization and support to the lateral cut guide 400 during a cuttingoperation to provide increased cutting accuracy. Additionally, asindicated above, the concave region 405 of the lateral guiding portion404 is intended to serve as a soft tissue retractor to facilitatecreation of space for entry of the sawblade into the lateral cuttingguide channel 430 to avoid damage or trauma to the soft tissue.

Once the lateral cut guide 400 is positioned and oriented relative tothe datum block 100, the pinch force mechanism 106 may be actuated tolock the lateral cut guide 400 in a position relative to the datum block100. Actuation of the pinch force mechanism 106 correspondinglycompresses the planar superior surface 418 of the inferior mountingplate 414 against the planar inferior surface 152 of the reference bench104 to thereby capture/lock the lateral cut guide 400 to the datum block100, which in turn retains the lateral cut guide 400 in a fixed positionand orientation relative to the datum block 100. As should beappreciated, locking of the lateral cut guide 400 maintains the lateralcutting guide 430 in a fixed inferior-superior position relative to thedatum block 100, which in turn provides increased cutting accuracy.

After the lateral cut guide 400 is properly aligned and positionedrelate to the datum block 100 and engaged with the datum block 100 viaactuation of the pinch force mechanism 106, an oscillating orreciprocating saw (or another cutting device) is inserted into anddisplaced along the lateral cutting guide 430 to form the horizontallateral resection cut C_(HL) in the proximal tibia 12 (FIG. 29B) tocomplete the lateral resection of the proximal tibia 12. As should beappreciated, positioning of the elongate pin portion 442 of the tibialpin 406 into the previously-formed lateral pin opening O_(L) serves as aguard or stop to control the depth of the horizontal lateral resectioncut C_(HL) and to prevent overcutting or notching of the tibial eminence14 which might otherwise compromise the strength and integrity of thetibial eminence 14. In addition to serving as a protective guard orstop, the tibial pin 406 also provides additional stabilization andsupport to the lateral cut guide 400 during the cutting operation toprovide increased cutting accuracy. Although the illustrated embodimentof the elongate pin portion 442 does not extend across the entireanterior-posterior dimension of the proximal tibia 12, it should beunderstood that other lengths of the elongate pin portion 442 may beused that extend across substantially the entire anterior-posteriordimension of the proximal tibia 12.

As should be appreciated, the combined use of the eminence stylus 300(described above) and the lateral cut guide 400 allows for the formationof all necessary resection cuts to complete medial and lateral resectionof the proximal tibia 12. As should also be appreciated, since theeminence stylus 300 and the lateral cut guide 400 are both locked to thedatum block 100 in the same manner using a constant reference plane(i.e., by compressing a planar mounting plate against the inferiorsurface 152 of the reference bench 104), it is possible to ensure thatthe horizontal medial resection cut C_(HM) (formed via use of theeminence stylus 300) and the horizontal lateral resection cut C_(HL)(formed via use of the lateral cut guide 400) are co-planar to oneanother.

F. Saw Capture Block

Referring to FIG. 30, shown therein is a saw capture block 500 accordingto one form of the present invention, as attached to the datum block100. However, it should be understood that the saw capture block 500 mayalso be attached to and used in association with the recut block 600(discussed below) or other devices or instruments. In the illustratedembodiment, the saw capture block 500 is attached to the datum block 100via the locking or pinch force mechanism 106 of the datum block 100,details of which have been set forth above. Additionally, although notillustrated in FIG. 30, it should be understood that the datum block 100is initially attached to the proximal tibia 12 via the provisionalattachment pin 190 and/or the terminal attachment pins 196 (FIG. 10)prior to attachment of the saw capture block 500 to the datum block 100.

The saw capture block 500 includes features that cooperate with featuresof the datum block 100 (or the recut block 600) to provide a saw captureor cutting guide channel that guides an oscillating or reciprocating saw(or another type of cutting instrument) along a cutting plane to form ahorizontal resection cut in the proximal tibia 12. In one embodiment,the saw capture block 500 may be used in association with the datumblock 100 (or the recut block 600) to perform a total or full resectionof the proximal tibia 12 (i.e., the complete removal of a proximalregion of the proximal tibia 12 to form a planar resection cut extendingentirely across the proximal tibia 12). For example, the saw captureblock 500 may be particularly beneficial for use in association with CR(cruciate retaining) and PS (posteriorly stabilized) arthroplastyprocedures, although use of the saw capture block 500 in associationwith other knee arthroplasty procedures is also contemplated.

Referring collectively to FIGS. 31, 32A and 32B, in the illustratedembodiment, the saw capture block 500 is a single-piece monolithicstructure including an inferior mounting portion 502 and a superiorguide portion 504. In one embodiment, the inferior mounting portion 502and the superior guide portion 504 are formed as a single piece toprovide the saw capture block 500 as a single-piece monolithicstructure. However, in other embodiments, the inferior mounting portion502 and the superior guide portion 504 may be formed separately from oneanother and integrated together to form a multi-piece saw capture blockassembly.

In one embodiment, the inferior mounting portion 502 has a plate-likeconfiguration defining substantially flat/planar superior and inferiorsurfaces 510, 512, respectively. Additionally, in a further embodiment,the inferior mounting plate 502 has a trapezoidal shape and defines anouter perimeter sized and configured for general alignment with an outerperimeter of the superior portion 110 of the main body 102 of the datumblock 100 (FIG. 6E). As should be appreciated, alignment of the anteriorregion of the inferior mounting plate 502 with the anterior region ofthe superior portion 110 aids in proper alignment and positioning of thesaw capture block 500 relative to the datum block 100 (FIG. 30).However, other shapes and configurations of the inferior mounting plate502 are also contemplated. Additionally, an alignment mark or lineindicia 514 extending in a medial-lateral direction is defined along thesuperior surface 510 of the inferior mounting plate 502 (FIG. 31) whichmay be aligned with the anterior edge of the reference bench 104 of thedatum block 100 to further aid in alignment and positioning of the sawcapture block 500 relative to the datum block 100 (FIG. 30).

The inferior surface 512 of the inferior mounting plate 502 may beprovided with a recess or indentation 516 (FIG. 32B) that is generallyalignable with the gripper member 180 associated with the pinch forcemechanism 106 of the datum block 100 when the saw capture block 500 ispositioned in general alignment on the datum block 100. As should beappreciated, the recess 514 has an inner cross section that is sizedsomewhat larger than the outer cross section of the gripper member 180such that when the pinch force mechanism 106 is partially actuated(i.e., positioning of the lever arm 160 at a pivotal location betweenthe fully locked and fully unlocked positions), the gripper member 180is partially received within the recess 516, but is not compressedtightly against the mounting plate portion 502. In this operationalconfiguration the saw capture block 500 is provisionally retained on thedatum block 100, but is not securely locked to the datum block 100. Thesaw capture block 500 is therefore permitted to rotate relative to thedatum block 100 and translate relative to the datum block 100 within theconfines of the recess 516 (i.e., translation is limited by abutment ofthe gripper member 180 against the inner parametrical surfaces 518 ofthe recess 516). Use of this provisionally retained configuration may beparticularly beneficial during a cutting operation to allow a widerrange of motion of the cutting instrument relative to the proximal tibia12, while still maintaining engagement of the saw capture block 500 withthe datum block 100. However, at any point in the cutting operation, thesaw capture block 500 may be locked in position on the datum block 100by fully actuating the pinch force mechanism 106 to lock the saw captureblock 500 in position.

Additionally, it should be understood that in other embodiments,engagement between the saw capture block 500 and the datum block 100 isfully constrained and does not allow any relative movement between thesaw capture block 500 and the datum block 100. As should be appreciated,compressed engagement of the gripper member 180 against the mountingplate portion 502 via full actuation of the pinch force mechanism 106,in combination with engagement between three mating surface pairsdefined between the saw capture block 500 and the datum block 100, fullyand securely constrains the saw capture block 500 in position relativeto the datum block 100. As shown in FIG. 33C, in the illustratedembodiment, the three mating surface pairs between the saw capture block500 and the datum block 100 include mating engagement of the inferiorplanar surface defined by mounting plate 502 of the saw capture block500 with the superior planar surface defined by the superior portion 110of the datum block 100, mating engagement of the superior planar surfacedefined by the mounting plate 502 of the saw capture block 500 with theinferior planar surface defined by the reference table 104 of the datumblock 100, and mating engagement of the medially-facing edge of themounting leg 522 (FIG. 32A) of the saw capture block 500 with thelaterally-facing edge defined by the reference table 104 of the datumblock 100. However, other mating surface pairs defined between the sawcapture block 500 and the datum block 100 are also contemplated.

In one embodiment, the superior capture or guide portion 504 has a guideplate portion 520 and a mounting leg portion 522 extending between andinterconnecting the guide plate portion 520 and the inferior mountingplate 502. The guide plate portion 520 defines substantially flat/planarsuperior and inferior surfaces 524, 526, respectively, and has agenerally trapezoidal shape defining an outer perimeter sized andconfigured for general alignment with an outer perimeter of thereference bench 104 of the datum block 100 (FIG. 6E). Alignment of theouter perimeter of the guide plate 520 with the outer perimeter of thereference bench 104 may further aid in proper alignment and positioningof the saw capture block 500 relative to the datum block 100 (FIG. 30).However, other shapes and configurations of the guide plate 520 are alsocontemplated. The mounting leg 522 includes a spacer portion 522 aattached to the inferior surface 526 of the guide plate 520, and a baseportion 522 b that is attached to the superior surface 510 of theinferior mounting plate 502. A guide slot 528 is defined between theinferior surface 526 of the guide plate 520 and a superior surface ofthe mounting leg base portion 522 b.

Referring collectively to FIGS. 30 and 33A-33C, shown therein is the sawcapture block 500 attached to the datum block 100. Having described thestructural features associated with the saw capture block 500, some ofthe operational characteristics associated with the saw capture block500 according to various embodiments of the present invention will nowbe discussed.

The saw capture block 500 is initially engaged to the datum block 100 bypositioning the inferior mounting plate 502 into the slot or channel 154defined between the reference bench 104 and the main body 102 of thedatum block 100. In this initial engagement arrangement, the positionand orientation of the saw capture block 500 may be adjusted relative tothe datum block 100. As indicated above, various features associatedwith the saw capture block 500 may be used to properly position andorient the saw capture block 500 relative to the datum block 100. Forexample, alignment of the mark or line indicia 514 defined along thesuperior surface 510 of the inferior mounting plate 502 with theanterior edge of the bench 104 may aid in properly positioning andorienting the saw capture block 500 relative to the datum block 100.Additionally, alignment of the anterior perimeter of the inferiormounting plate 502 with the anterior region of the superior portion 110of the datum block 100, as well as alignment of the outer perimeter ofthe guide plate 520 with the outer perimeter of the reference bench 104,may further aid in properly positioning and orienting the saw captureblock 500 relative to the datum block 100. Once the saw capture block500 is properly positioned and oriented relative to the datum block 100,the pinch force mechanism 106 may be actuated to lock the saw captureblock 500 in a position relative to the datum block 100. Actuation ofthe pinch force mechanism 106 correspondingly compresses the planarsuperior surface 510 of the inferior mounting plate 502 against theplanar inferior surface 152 of the reference bench 104 to therebycapture/lock the saw capture block 500 to the datum block 100, which inturn retains the saw capture block 500 in a fixed position andorientation relative to the datum block 100. As should be appreciated,locking of the saw capture block 500 in a fixed inferior-superiorposition relative to the datum block 100 provides a fixed saw captureguide between the saw capture block 500 and the datum block 100.

As shown most clearly in FIGS. 30 and 33C, when the saw capture block500 is engaged with the datum block 100, the planar inferior surface 526of the guide plate 520 is aligned substantially parallel with and offsetfrom the planar superior surface 150 of the reference bench 104 tothereby form a medial-lateral cutting guide or channel 530 definedbetween the adjacent inferior and superior planar surfaces 526, 150. Asshould be appreciated, the medial-lateral cutting guide 530 preferablydefines a channel width sized in relatively close tolerance with thecutting blade thickness of an oscillating or reciprocating saw (oranother cutting device) to form a smooth and accurate resection cutalong the proximal tibia 12. Additionally, the width of the guide slot528 defined between the inferior surface 526 of the guide plate 520 andthe superior surface of the mounting leg base portion 522 b (FIG. 32A)is equal to the distance separating the inferior and superior planarsurfaces 526, 150 to thereby provide the medial-lateral cutting guide530 with a uniform channel width entirely along the medial-lateraldimension of the saw capture block 500.

After the saw capture block 500 is properly aligned and positionedrelate to the datum block 100 and engaged with the datum block 100 viaactuation of the pinch force mechanism 106, an oscillating orreciprocating saw (or another cutting device) is inserted into anddisplaced along the medial-lateral cutting guide 530 to fully resect theproximal tibia 12. As shown in FIG. 33C, the cutting guide 530 is openand unrestricted along the anterior and posterior sides and along themedial side of the cutting guide 530. Additionally, as shown in FIG.33A, the cutting guide 530 is open and unrestricted along the posteriorregion along the lateral side of the cutting guide 530, with theanterior region along the lateral side being blocked by the mounting leg522 of the saw capture block 500. However, the open posterior regionalong the lateral side of the cutting guide 530 provides a pathway forthe saw to fully resect the proximal tibia 12. However, as indicatedabove, if additional access to the proximal tibia 12 is required, thepinch force mechanism 106 may be positioned in a partially actuatedposition wherein the saw capture block 500 is provisionally retained onthe datum block 100, but is permitted to rotate and translate (within aconfined range) relative to the datum block 100 to allow for a widerrange of motion of the saw or cutting instrument. Following resection ofthe proximal tibia 12, the saw capture block 500 may be removed from thedatum block 100 to allow for engagement of other devices and instrumentsto the datum block 100.

G. Recut Block

Referring to FIGS. 34 and 35, shown therein is a recut block 600according to one form of the present invention, as shown in relation tothe proximal tibia 12. In the illustrated embodiment, the recut block600 is attached to the proximal tibia 12 using the terminal attachmentpins 196 a, 196 b previously used to attach the datum block 100 to theproximal tibia 12 (FIG. 10), the details of which will be set forthbelow. Accordingly, the position and orientation of the recut block 600relative to the proximal tibia 12 is advantageously based on the samepoints of reference used to set the position and orientation of thedatum block 100. However, other techniques and devices for attaching therecut block 600 to the proximal tibia 12 are also contemplated.

As will also be set forth in greater detail below, thereference/resection plane (i.e., the planar superior surface of thereference bench) defined by the recut block 600 may be varied/angledrelative to the horizontal reference/resection plane defined by thedatum block 100. Accordingly, should a change to the horizontal medialresection cut C_(HM) and/or the horizontal lateral resection cut C_(HL)be desired (i.e., a different posterior slope angle, varus-valgus angle,or both), the datum block 100 can be removed from the terminalattachment pins 196 a, 196 b and replaced with a recut block 600defining the appropriate reference/resection plane to recut one or bothof the horizontal resection cuts to the desired angle. As should beappreciated, a kit or set containing multiple recut blocks 600 definingdifferent reference/resection planes (i.e., different posterior slopeangles, varus-valgus angles, or both) can be provided to accommodateintra-operative changes/alterations to the horizontal medial resectioncut C_(HM) and/or the horizontal lateral resection cut C_(HL).

Similar to the datum block 100, the recut block 600 is used as afundamental instrument to provide a neutral/reference tibial foundationto which other devices or instruments may be engaged to and referencedfrom. Additionally, the recut block 600 is designed to be substantiallyinterchangeable with the datum block 100. Accordingly, any device orinstrument that is used in association with the datum block 100 may alsobe used in association with the recut block 600. Therefore, if the datumblock 100 is replaced with the recut block 600 to recut one or both ofthe horizontal resection cuts at a different angle, subsequent steps andtechniques associated with the knee arthroplasty procedure which utilizeother devices and instruments can be performed using the recut block600.

As indicated above, the recut block 600 is attached to the proximaltibia 12 using the terminal attachment pins 196 a, 196 b previously usedto attach the datum block 100 to the proximal tibia 12 (FIGS. 34 and35). Notably, it is not necessary to remove the terminal attachment pins196 a, 196 b from the proximal tibia 12 to detach the datum block 100from the proximal tibia 12 or to attach the recut block 600 to theproximal tibia 12. Instead, referring back to FIG. 10, the provisionalattachment pin 190 is removed from the proximal tibia 12 and the datumblock 100 is simply slipped off of the terminal attachment pins 196 a,196 b. Since the recut block 600 is interchangeable with the datum block100, the recut block 600 is slipped over the proximal heads 198 of theterminal attachment pins 196 a, 196 b (via the same pin-receivingopenings that were used to attach the datum block 100 to the proximaltibia 12) and displaced along the pins 196 a, 196 b until positionedadjacent the proximal tibia 12. Since the recut block 600 is attached tothe proximal tibia 12 using the identical points of reference (the pins196 a, 196 b) used to attach the datum block 100 to the proximal tibia12, the position and orientation of the recut block 600 relative to theproximal tibia 12 can be set to match that of the datum block 100 (withthe exception of defining a different horizontal reference/resectionplane). If desired, a third terminal attachment pin may be inserted intoanother of the pin-receiving openings and driven into the proximal tibiaat an oblique angle relative to the pins 196 a, 196 b to retain therecut block 600 in position adjacent the proximal tibia 12.Alternatively, a third terminal attachment pin having an enlarged head(like the provisional attachment pin 190) may be inserted into anotherof the pin-receiving openings and driven into the proximal tibia 12until the enlarged head is compressed against the recut block 600 toretain the recut block 600 in position adjacent the proximal tibia 12.

Referring collectively to FIGS. 36A-36F, shown therein are furtherdetails associated with the recut block 600. The recut block 600generally includes a main body 602 configured for attachment to theproximal tibia 12, a reference bench or table 604 extending from themain body 602 and configured for removable attachment of variousdevices/instruments to the recut block 600, and a locking mechanism 606associated with the main body 602 and configured to removably lock theother devices/instruments to the recut block 600. In the illustratedembodiment, the recut block 600 is not configured to engage and supportan extramedullary alignment rod (such as the alignment rod 108associated with the datum block 100). However, in other embodiments, therecut block 600 may be configured to engage and support anextramedullary alignment rod or other types of alignment devices.

In the illustrated embodiment, the main body 602 of the recut block 600is configured as a single-piece monolithic connection block 610 defininga substantially flat/planar superior surface 612, a laterally facingsurface 614, a cavity 616 (FIG. 34) extending through the connectionblock 610 from the planar superior surface 612 in a superior-inferiordirection, and a passage 618 (FIG. 36C) extending through the connectionblock 610 in an anterior-posterior direction and transverselyintersecting and positioned in communication with the cavity 616. Aswill be discussed in greater detail below, the cavity 616 and thepassage 618 serve to house components of the locking mechanism 606. Theconnection block 610 has a generally rectangular shape configuredsimilar to that of the superior portion 110 of the datum block 100.However, other shapes and configuration are also contemplated.

The connection block 610 further defines a plurality of pin-receivingopenings 622 extending therethrough generally in an anterior-posteriordirection that are sized and configured for receipt of the terminalattachment pins 196 a, 196 b anchored to the proximal tibia 12 or forreceipt of additional attachment pins. As should be appreciated, thepin-receiving openings 622 defined in the recut block 600 have the samerelative position and orientation as the pin-receiving openings 122defined in the datum block 100 such the recut block 600 may beinterchanged with the datum block 100 using the same terminal attachmentpins 196 a, 196 b previously used to attach the datum block 100 to theproximal tibia 12.

As indicated above, the recut block 600 includes a reference bench ortable 604 extending from the main body 602 and configured for removableattachment of various devices/instruments to the recut block 600. In theillustrated embodiment, the reference bench 604 is formed unitarily withthe main body 602 to define a single-piece monolithic structure.However, in other embodiments, the reference bench 604 may be formedseparately from the main body 602 and coupled thereto to define anintegrated multi-piece structure. As shown in FIG. 36E, the referencebench 604 has a non-rectangular trapezoidal shape configured similar tothat of the reference bench 104 of the datum block 100, defining anarrowing or tapered width extending away from the main body 602 in amedial-lateral direction. However, other suitable shapes andconfigurations of the reference bench 604 are also contemplated asfalling within the scope of the present invention.

As shown in FIGS. 36A-36C, the reference bench 604 defines asubstantially flat/planar superior surface 650 and a substantiallyflat/planar inferior surface 652, with the planar superior and inferiorsurfaces 650, 652 preferably arranged generally parallel with oneanother, although non-parallel arrangements of the planar superior andinferior surfaces 650, 652 are also contemplated. Additionally, theplanar inferior surface 652 of the reference bench 604 is positionedopposite the planar superior surface 612 of the connection block 610 tothereby define a space or gap 654 therebetween sized and configured forreceipt of plate-like portions of other devices and instruments to beconnected with the recut block 600, details of which will be set forthbelow. In the illustrated embodiment, the planar inferior surface 652 ofthe reference bench 604 is preferably arranged generally parallel withthe planar superior surface 612 of the connection block 610, althoughnon-parallel arrangements of the opposing superior and inferior surfacesare also contemplated. Additionally, although not specificallyillustrated in the drawing figures, the reference bench 604 may beprovided with a groove or indicia extending along the planar superiorsurface 650 in an anterior-posterior direction to provide a visualindication or marker corresponding to the location of the verticalmedial resection C_(VM) of the proximal tibia 12 (i.e., similar to thegroove/indicia 156 defined along the reference table 104 of the datumblock 100).

As discussed above and as illustrated in FIG. 36A-36C, the recut block600 defines a reference/resection plane P extending along the planarsuperior surface 650 of the reference bench 604. As also discussedabove, the reference/resection plane P of the recut block 600 may bevaried/angled relative to the horizontal reference/resection plane ofthe datum block 100 (as defined along the planar superior surface 150 ofthe reference bench 104). Accordingly, should a change to the previouslycut horizontal medial resection cut C_(HM) and/or the horizontal lateralresection cut C_(HL) (formed using the datum block 100) be desired(i.e., having a different posterior slope angle, varus-valgus angle, orboth), the datum block 100 can be replaced with a recut block 600defining the appropriate reference/resection plane P to recut one orboth of the horizontal resection cuts to the desired angle. For example,as illustrated in FIG. 36A, the planar superior surface 650 of the recutblock 600 may be provided with a reference/resection plane P having aposterior slope angle β that varies from the horizontalreference/resection plane of the datum block 100 within the range of +βto −β. Additionally, as illustrated in FIG. 36B, the planar superiorsurface 650 of the recut block 600 may be provided with areference/resection plane P having a varus-valgus angle θ that variesfrom the horizontal reference/resection plane of the datum block 100within the range of +θ to −θ. In other embodiments, the planar superiorsurface 650 of the recut block 600 may be provided with areference/resection plane P having a varus-valgus angle θ and aposterior slope angle θ that both vary from the horizontalreference/resection plane of the datum block 100.

As also discussed above, a kit or set containing multiple recut blocks600 defining varying reference/resection planes can be provided toaccommodate intra-operative changes/alterations to the horizontal medialresection cut C_(HM) and/or the horizontal lateral resection cut C_(HL).For example, the kit may include multiple recut blocks 600 definingreference/resection planes P having a posterior slope angle β of +2°,+4°, +6°, −2°, −4°, −6°, etc., or any other posterior slope angle β thatmay be used in a knee arthroplasty procedure to form a horizontal medialresection cut C_(HM) and/or the horizontal lateral resection cut C_(H)having a desired posterior slope angle. The kit may also includemultiple recut blocks 600 defining reference/resection planes P having avarus-valgus angle θ of +2°, +4°, +6°, −2°, −4°, −6°, etc., or any othervarus-valgus angle θ that may be used in a knee arthroplasty procedureto form a horizontal medial resection cut C_(HM) and/or the horizontallateral resection cut C_(H) having a desired varus-valgus angle.Additionally, providing the kit with further recut blocks 600 definingreference/resection planes P exhibiting other desired features andcharacteristics is also contemplated as falling within the scope of thepresent invention.

As indicated above, the recut block 600 includes a locking mechanism 606associated with the main body 602 that is configured to removably lockvarious devices/instruments to the reference bench 604. Referring toFIGS. 37A and 37B, illustrated therein are unlocked and lockedconfigurations of the recut block 600, respectively. Additionally,referring to FIGS. 38A and 38B, illustrated therein are correspondingunlocked and locked configurations of the locking mechanism 606,respectively.

In the illustrated embodiment, the locking mechanism 606 generallyincludes a threaded member or bolt-type actuator member 660 threadedlyengaged within the anterior-posterior passage 618 in the connectionblock 610 of the recut block 600, and a gripper member or actuatedmember 680 positioned within the inferior-superior cavity 616 in theconnection block 610 and movably engaged with the threaded member 660,the details of which will be set forth below. The main body 602 of therecut block 600 includes additional elements and features associatedwith the locking mechanism 606. For example, the connection block 610defines a circular opening 624 (FIG. 36F) extending through a posteriorwall of the connection block 610 in communication and general alignmentwith the anterior-posterior passage 618 that is sized to receive adistal end portion of the threaded member 660 therein to thereby act asa bearing surface to provide additional support and stability to thelocking mechanism 606. Additionally, a retaining pin 626 (FIGS. 36D and36E) at least partially extends into the anterior-posterior passage 618to prevent the threaded member 660 from backing entirely out of thepassage 618. A visualization slot or window 628 (FIG. 36D) also extendsthrough the inferior surface of the connection block 610 incommunication with the passage 618 to provide direct visualization ofand access to the components of the locking mechanism 606.

Referring specifically to FIGS. 37A/37B and 38A/38B, illustrated thereinare unlocked and locked configurations of the recut block 600 and thelocking mechanism 606. In the unlocked configuration shown in FIGS.37A/38A, a plate-like portion of a device/instrument may be positionedwithin the space or gap 654 defined between the planar inferior surface652 of the reference bench 604 and the planar superior surface 612 ofthe connection block 610. The recut block 600 and the locking mechanismmay then be transitioned from the unlocked configuration illustrated inFIGS. 37A/38A to the locked configuration illustrated in FIGS. 37B/38Bvia actuation of the locking mechanism 606. Actuation of the lockingmechanism 606 is accomplished by rotating the threaded member 660 tothreadingly displace the threaded member 660 along theanterior-posterior passage 618 in the direction of arrow A, which inturn displaces the gripper member 680 in an inferior-superior directionalong the cavity 616 in the direction of arrow B, and correspondinglyengages the gripper member 680 against the plate-like portion of thedevice/instrument positioned within the gap 654 and compresses theplate-like portion against the planar inferior surface 652 of thereference bench 604 to thereby retain the device/instrument in a fixedposition and orientation relative to the recut block 600.

Referring to FIGS. 39A-39D, shown therein are further details regardingthe locking mechanism 606 including the threaded member 660 and thegripper member 680. In the illustrated embodiment, the threaded member660 generally includes a proximal head portion 662, a threaded portion664, a tapered portion 666 and a distal stem portion 668. The proximalhead portion 662 includes one or more drive features 670 thatfacilitates receipt of a rotational force or torque onto the threadedmember 660. In one embodiment, the drive feature 670 comprises ahexagonal-shaped recess formed in the proximal head portion 662.However, other types and configurations of suitable drive features arealso contemplated. The threaded portion 664 includes external threads672 that are configured for threading engagement with internal threads(not shown) formed along the anterior-posterior passage 618 in theconnection block 610. Additionally, the threaded portion 664 may beprovided with an unthreaded portion 674 adjacent the location where thethreaded member 660 engages the gripper member 680 to avoid interferencebetween the external threads 672 and the gripper member 680. The taperedportion 666 defines a tapered outer surface 676 that is inwardly taperedin a proximal-distal direction. The distal stem portion 668 includes asubstantially smooth cylindrical-shaped shaft that extends through aguide channel formed in the gripper member 680 and which is positionedwithin the circular opening 624 (FIG. 36F) extending through theposterior wall of the connection block 610 to thereby act as a bearingto provide additional support and stability to the locking mechanism606, and particularly to the threaded member 660. Although a particularconfiguration of the threaded member 660 has been illustrated anddescribed herein, other configurations of actuator members, includingnon-threaded actuator members, are also contemplated for use inassociation with the locking mechanism 606.

In the illustrated embodiment, the gripper member 680 generally includesan inferior bearing portion 682 and a superior gripping portion 684. Theinferior bearing portion 682 includes a channel 686 extendingtherethrough in an anterior-posterior direction and which is sized toreceive the tapered portion 666 and the distal stem portion 668 of thethreaded member therein. The channel 686 is partially bound by one ormore bearing surfaces 688 configured for sliding engagement with thetapered surface 676 of the threaded member 660. The bearing surfaces 688may be angled to define an inward taper extending in ananterior-to-posterior direction. However, non-tapered bearing surfaces688 are also contemplated. Additionally the channel 686 narrows adjacentthe posterior end of the gripper member 680 to define a guide slot 690sized to received the distal stem portion 668 of the threaded member 660therein to stabilize engagement between the gripper member 680 and thethreaded member 660 and to allow the threaded member 660 to be linearlydisplaced along the channel 686. The superior gripping portion 684 ofthe gripper member may be provided with a generally circular outer crosssection sized for guiding displacement within the inferior-superiorcavity 616 in the connection block 610 generally along the arrow B. Thegripping portion 684 also includes a superior gripping surface 692configured for compressed engagement against plate-like portions ofdevices/instruments positioned within the gap 654 defined between thereference bench 604 and the connection block 610 of the recut block 600.

As indicated above, the recut block 600 and the locking mechanism aretransitioned from the unlocked configuration illustrated in FIGS.37A/38A to the locked configuration illustrated in FIGS. 37B/38B viaactuation of the locking mechanism 606 which is accomplished by rotatingthe threaded member 660 using a hex driver or another type of driverinstrument to threadingly displace the threaded member 600 along athreaded portion of the passage 618 in the connection block 610 in thedirection of arrow A. Displacement of the threaded member 660 in thedirection of arrow B slidably displaces the tapered surface 676 of thethreaded member 660 along the bearing surfaces 688 of the gripper member680, which in turn displaces the gripper member 680 along the cavity 616in the connection block 610 in the direction of arrow B. As should beappreciated, the sliding interaction between the tapered surface 676 andthe bearing surfaces 688 converts linear displacement of the threadedmember 660 in the direction of arrow A into liner displacement of thegripper member 680 in the direction of arrow B. Liner displacement ofthe gripper member 680 in the direction of arrow B in turn compresses aplate-like portion of device/instruments positioned within the gap 654defined between the reference bench 604 and the connection block 610against the planar inferior surface 652 of the reference bench 604 tothereby lock/retain the device/instrument in a fixed position andorientation relative to the recut block 600.

As should be appreciated, the compression or clamping force exerted bythe gripper member 680 onto the plate-like portion of thedevice/instrument positioned within the space 654 is controlled byincremental threading insertion or retraction of the threaded member 660into and out of the passage 618 in the connection block 610. Althoughthe illustrated embodiment of the locking mechanism 606 uses a hexdriver (not shown) to drive the threaded member 660 into and out of thepassage 618. However, other embodiments are also contemplated whereinthe threaded member 660 may be rotated via a thumb wheel or a T-shapedhandle that may be incorporated into the bolt-type actuator 660 to avoidthe need for a separate driver instrument. Although a particular typeand configuration of the locking mechanism 606 has been illustrated anddescribed herein for use in association with the recut block 600, itshould be understood that other types and configurations of lockingmechanisms or other compression structures/devices are also contemplatedfor use in association with the present invention in addition to or inlieu of the locking mechanism 606 including, for example, the pinchforce mechanism 106 illustrated and described above with regard to thedatum block 100.

H. Tibia Size Gauge

Referring to FIG. 40, shown therein is a tibia size gauge 700 accordingto one form of the present invention. As will be discussed in greaterdetail below, the tibia size gauge 700 may be used to reference/measuremedial and/or lateral aspects of the proximal tibia 12 along the tibialcortex (e.g., at the medial tibial cortex 12 _(MC) and/or at the lateraltibial cortex 12 _(LC)) at the proposed/intended level of the horizontalresection cuts. In this manner, the tibial baseplate implant I may beappropriately sized, and the resulting position of the tibial baseplateimplant I (FIGS. 41C and 42C) may be appropriately centered on theresected proximal tibia 12 in a medial-lateral direction to minimizeunderhang/overhang of the baseplate implant I relative to the outerperiphery of the resected proximal tibia 12, which in turn results in astronger and more secure and stable engagement of the tibial implant onthe proximal tibia.

As shown in FIG. 40, the tibia size gauge 700 is used in associationwith the eminence stylus 300 attached to the datum block 100, with thedatum block 100 in turn pinned to the proximal tibia 12, the details ofwhich have been illustrated and described above. However, it should beappreciated that the tibia size gauge 700 may also be used inassociation other devices and instruments, including but not limited tothe eminence stylus 300′ illustrated and described above.

The tibia size gauge 700 generally includes a scaled reference or datumplate 710 having a length extending generally along a longitudinal axisL, a first reference arm 720 extending axially from the scaled datumplate 710 and including a distal pointer 722 defining a distal endsurface 724 configured for engagement with an outer surface of theproximal tibia 12, and a second reference arm 730 transversely offsetfrom the scaled plate 710 by a transversely extending spacer arm 740 andincluding a distal pointer 732 defining a distal end surface 734configured for engagement with an outer surface of the proximal tibia12. In the illustrated embodiment, the tibia size gauge 700 is providedas a single-piece, substantially flat/planar plate having a generallyuniform and relatively thin plate thickness t (FIG. 40). However, otherembodiments are also contemplated wherein the tibia size gauge 700 maytake on other configurations and/or may be provided as multiple piecesor elements that are interconnected with one another to form the tibiasize gauge 700. Additionally, in the illustrated embodiment, the firstand second reference arms 720, 730 are oriented at an oblique anglerelative to the longitudinal axis L of the scaled datum plate 710.However, in other embodiments, the first and second reference arms 720,730 may be arranged generally parallel with the longitudinal axis L.Further, in the illustrated embodiment, the distal end surfaces 724, 734of the distal pointers 722, 732 are curved or rounded to provide secureand stable engagement with an outer surface of the proximal tibia 12.However, in other embodiments, the distal end surfaces 724, 734 may beprovided with a pointed configuration or a blunt configuration.

In the illustrated embodiment, the scaled datum plate 710 is configuredfor positioning within the medial cutting guide 348 which, as discussedabove in association with FIGS. 20A-20C, is used to form the medialhorizontal resection cut C_(HM) in the proximal tibia 12. As alsodiscussed above, the medial cutting guide 348 is formed between theplanar inferior surface 346 defined by the cutting guide flange 316 onthe eminence stylus 300 and the planar superior surface 150 defined bythe reference bench 104 on the datum block 100. As should beappreciated, the superior-inferior location of the medial cutting guide348 (which is dictated by the inferior-superior location of the datumblock 100 on the proximal tibia 12) determines the level/location of thehorizontal medial and lateral resection cuts C_(HM), C_(HL), and theinternal-external angular orientation of the eminence stylus 300dictates the internal-external angular orientation of the medial cuttingguide 348 and the resulting orientation of the vertical medial andlateral resection cuts C_(VM), C_(VL). The thickness t (FIG. 40) of thescaled datum plate 710 is preferably sized in relatively close tolerancewith the width of the medial cutting guide 348 to maintain the scaleddatum plate 710 in a substantially co-planar relationship with thecutting plane defined by the medial cutting guide 348 (i.e., the planealong which the horizontal medial resection cut C_(HM) is formed).

As shown in FIG. 40, the scaled datum plate 710 includes one or moremeasurement scales 712 that each include scaled measurement indicia 714which serve to provide a visual indication as to the distances beingmeasured by the tibia size gauge 700. In the illustrated embodiment, thescaled measurement indicia 714 include a series of parallel lines 714 aand a series of numbers 714 b corresponding to the parallel lines 714 a.In one embodiment, the parallel lines 714 a alternate between solidlines and dashed lines to aid in indentifying/distinguishing which ofthe parallel lines 714 a is aligned with a predetermined measurementreference feature, which is the present embodiment is thestraight/planar medial edge 316 a defined by the cutting guide flange316 of the eminence stylus 300. However, it should be understood thatother measurement reference features are also contemplated. In a furtherembodiment, adjacent pairs of the numbers 714 b are offset from oneanother in an axial direction (along the longitudinal axis) to aid inindentifying/distinguishing which of the numbers 714 b is associatedwith the line that is aligned with the predetermined reference feature.Although one particular embodiment of the scaled measurement indicia 714has been illustrated and described herein, it should be understood thatother suitable types and configurations of measurement indicia are alsocontemplated for use in association with the tibia size gauge 700.

Additionally, in the illustrated embodiment, the tibia size gauge 700 isconfigured to provide measurements of medial and lateral aspects of theproximal tibia 12 (e.g., the medial tibial cortex 12 _(MC) and thelateral tibial cortex 12 _(LC); FIGS. 40/41A/42A). Additionally, thetibia size gauge 700 is configured to provide measurements associatedwith both the left knee and the right knee (i.e., the tibia size gauge700 is configured to be ambidextrous). Accordingly, the illustratedembodiment of the scaled datum plate 710 is provided with fourmeasurement scales 712 a, 712 b, 712 c and 712 d (FIGS. 41A/42A), withthe measurement scale 712 a associated with measurements of medialaspects of the left knee (“LM”), the measurement scale 712 b associatedwith measurements of lateral aspects of the left knee (“LL”), themeasurement scale 712 c associated with measurements of medial aspectsof the right knee (“RM”), and the measurement scale 712 d associatedwith measurements of lateral aspects of the right knee (“RL”). However,it should be understood that the tibia size gauge 700 may be providedwith any number of measurement scales 712 including, for example, asingle measurement scale.

Referring now to FIGS. 41A-41C, shown there is a technique according toone form of the invention for using the tibia size gauge 700 toreference/measure medial aspects of the proximal tibia 12 along thetibial cortex (e.g., at the medial tibial cortex 12 _(MC)) at theproposed/intended level of the horizontal resection cuts to determinethe appropriate size of the tibial baseplate implant I to be installedon the proximal tibia 12 subsequent to resection. As indicated above,the datum block 100 is initially pinned to the proximal tibia 12, andthe eminence stylus 300 is provisionally engaged to the datum block 100and centered/aligned in relation to the proximal tibia 12 or otheranatomic structures using the indicator members 306 a, 306 b, thealignment rod 18 and/or other alignment structures or alignmenttechniques. Once the eminence stylus 300 is centered/aligned in relationto the proximal tibia 12, the eminence stylus 300 is locked in positionon the datum block 100 via the pinch lock mechanism 106. As indicatedabove, the proposed/intended level of the horizontal resection cutscorresponds to the cutting plane defined by the medial cutting guide348.

The scaled datum plate 710 of the tibia size gauge 700 is positionedwithin the medial cutting guide 348, with the measurement scale 712 aassociated with measurements of medial aspects of the left knee (i.e.,“LM”) positioned adjacent the straight/planar medial edge 316 a of thecutting guide flange 316. The distal end surface 724 of the pointer 722is then positioned in contact with the medial tibial cortex 12 _(MC) onthe medial side of the proximal tibia 12. While maintaining contactbetween the distal end surface 724 of the pointer 722 and the medialtibial cortex 12 _(MC), the user observes which of the parallel lines714 a on the measurement scale 712 is aligned with the straight/planarmedial edge 316 a of the cutting guide flange 316. The tibia size gauge700 may require a certain degree of internal-external rotation withinthe medial cutting guide 348 to obtain alignment between the appropriateline 714 a and the straight/planar medial edge 316 a. In the illustratedembodiment, the number 714 b corresponding to the line 714 a alignedwith the medial edge 316 a relates to the size of the tibial baseplateimplant I (FIGS. 41B and 41C) that would properly fit on the proximaltibia 12 subsequent to resection. As shown in FIG. 41A, the indicatedsize measurement is “4”, which corresponds to a size 4 tibial baseplateimplant I to be installed on the proximal tibia 12 (FIG. 41B). As shownin FIG. 41C, subsequent to resection and finishing of the proximal tibia12, the appropriately sized baseplate implant I is installed on theresected proximal tibia 12 wherein underhang/overhang of the baseplateimplant I on the resected proximal tibia 12 is minimized relative to theperipheral outer boundary of the proximal tibia 12 due to theabove-described implant sizing technique.

As discussed above, in the illustrated embodiment, the numbers 714 b onthe measurement scale 712 relate to the size of the tibial baseplateimplant I. However, in other embodiments, the numbers 714 b on themeasurement scale 712 may relate to the actual linear distance betweenthe medial tibial cortex 12 _(MC) in contact with the distal end surface724 of the pointer 722 and the centerline of the eminence stylus 300(i.e., the centerline between the indicator members 306 a, 306 b), whichpreferably corresponds to the anatomic medial-lateral center of theproximal tibia 12 at the proposed/intended level of resection.

In the measurement technique illustrated in FIGS. 41A-41C and describedabove, the appropriate size of the tibial baseplate implant I to beinstalled on the proximal tibia 12 is determined byreferencing/measuring medial aspects of the proximal tibia 12 along thetibial cortex (e.g., at medial tibial cortex 12 _(MC)) at theproposed/intended level of resection. However, referring to FIGS.42A-42C, it should be understood that the appropriate size of the tibialbaseplate implant I may also be determined by referencing/measuringlateral aspects of the proximal tibia 12 along the tibial cortex (e.g.,at the lateral tibial cortex 12 _(LC)) at the proposed/intended level ofresection. Specifically, once the eminence stylus 300 iscentered/aligned in relation to the proximal tibia 12, the scaled datumplate 710 of the tibia size gauge 700 is initially positioned within themedial cutting guide 348 with the second reference arm 730 extendingalong the lateral side of the proximal tibia 12 and with the distal endsurface 734 of the pointer 732 positioned in contact with the lateraltibial cortex 12 _(LC). Additionally, the measurement scale 712 bassociated with measurements of lateral aspects of the left knee (i.e.,“LL”) is positioned adjacent the straight/planar medial edge 316 a ofthe cutting guide flange 316. While maintaining contact between thedistal end surface 734 of the pointer 732 and the lateral tibial cortex12 _(LC), the user observes which of the parallel lines 714 a on themeasurement scale 712 is aligned with the straight/planar medial edge316 a of the cutting guide flange 316. As shown in FIG. 42A, theindicated size measurement is once again indicated as “4”, whichcorresponds to the size of the tibial baseplate implant I to beinstalled on the proximal tibia 12 (FIGS. 42B/42C) following resectionto minimize underhang/overhang of the baseplate implant I relative tothe peripheral outer boundary of the proximal tibia 12 at the level ofresection.

As indicated above, the tibia size gauge 700 is configured to beambidextrous, meaning the tibia size gauge 700 may also be used toreference/measure medial and lateral aspects of the proximal tibia 12associated with both the left knee and the right knee. As should beappreciated, when referencing/measuring medial and lateral aspects ofthe proximal tibia 12 associated with the left knee, the measurementscales 712 a, 712 b associated with measurements of medial aspects ofthe left knee (i.e., “LM”) and lateral aspects of the left knee (i.e.,“LL”) are used. However, when referencing/measuring medial and lateralaspects of the proximal tibia 12 associated the right knee, themeasurement scales 712 c, 712 d associated with measurements of medialaspects of the right knee (i.e., “RM”) and lateral aspects of the rightknee (i.e., “RL”) are used.

Referring collectively to FIGS. 41A-41C and FIGS. 42A-42C, a techniqueaccording to a further form of the invention may be used to ensure thatthe appropriately sized tibial baseplate implant I is centered on theresected proximal tibia 12 (i.e., the centerline C of the implant I isaligned with the true anatomic center of the proximal tibia 12 at theproposed/intended level of the horizontal resection cuts). Notably,determining the true anatomic center of the proximal tibia 12 at theproposed/intended level of resection may be used to ensure the correctposition of the horizontal resection cuts (i.e., that the resection cutsare centered relative to the true anatomic center of the proximal tibia12), which in turn dictates the ultimate position of the baseplateimplant I on the proximal tibia 12. The disclosed centering techniquereferences/measures both medial and lateral aspects of the proximaltibia 12 along the tibial cortex (e.g., at the medial tibial cortex 12_(MC) and at the lateral tibial cortex 12 _(LC)) at theproposed/intended level of resection, and uses the resultingmeasurements to determine the true anatomic center of the proximal tibia12 at the proposed/intended level of resection, the details of whichwill be discussed below.

As discussed above and as shown in FIG. 41A, the tibia size gauge 700 isinitially used to reference/measure the medial tibial cortex 12 _(MC) atthe proposed/intended level of resection by observing which of theparallel lines 714 a on the measurement scale 712 a is aligned with thestraight/planar medial edge 316 a of the cutting guide flange 316. Asalso discussed above and as shown in FIG. 42A, the tibia size gauge 700may then be used to reference/measure the lateral tibial cortex 12 _(LC)at the proposed/intended level of resection by observing which of theparallel lines 714 a on the measurement scale 712 b is aligned with thestraight/planar medial edge 316 a of the cutting guide flange 316. Ifthe observed measurement associated with the referencing/measuring ofthe medial tibial cortex 12 _(MC) is equal to the observed measurementassociated with the referencing/measuring of the lateral tibial cortex12 _(LC), then the eminence stylus 300 is appropriately centered alongthe true anatomic center of the proximal tibia 12 at theproposed/intended level of resection, and the vertical resection cutscan then be made for receipt of the tibial baseplate implant I at theappropriately centered position on the resected proximal tibia 12.

However, if the observed medial and lateral measurements are not equalto one another, then the medial-lateral position and/or the orientationof the eminence stylus 300 can be correspondingly adjusted based on theobserved medial and lateral measurements to more closely align theeminence stylus 300 with the true anatomic center of the proximal tibia12 at the proposed/intended level of resection. For example, if theobserved medial measurement is “3” and the observed lateral measurementis “5”, then the eminence stylus 300 may be unlocked from the datumblock 100 and the position of the eminence stylus 300 shifted in alateral direction to more closely align the centerline of the eminencestylus 300 with the true anatomic center of the proximal tibia 12 at theproposed/intended level of resection. After the adjustment to theposition of the eminence stylus 300 is made, further medial and lateralmeasurements are once again taken and compared with one another todetermine if further adjustment to the position of the eminence stylus300 is required, or whether the true anatomic center has been reached.

As should be appreciated, this iterative measurement process using thetibia size gauge 700 to reference/measure both medial and lateralaspects of the proximal tibia 12 along the tibial cortex at theproposed/intended level of resection results in more accurate centeringof the eminence stylus 300 with the true anatomic center of the proximaltibia 12. As should be further appreciated, centering of the eminencestylus 300 with the true anatomic center of the proximal tibia 12results in the formation of correctly centered/positioned resectioncuts, which in turn ensures that the centerline C of the implant I isproperly aligned with the anatomic center of the proximal tibia 12 atthe resection level to thereby minimize underhang/overhang of theimplant I relative to the peripheral outer boundary of the proximaltibia 12 (FIGS. 41C/42C).

Referring to FIGS. 43-45, shown therein is a tibia size gauge 750according to another form of the present invention. Similar to the tibiasize gauge 700 illustrated and described above, the tibia size gauge 750may be used to reference/measure medial aspects of the proximal tibia 12along the tibial cortex (e.g., at the medial tibial cortex 12 _(MC)) atthe proposed/intended level of the horizontal resection cuts todetermine the appropriate size of the tibial baseplate implant I to beinstalled on the resected proximal tibia 12. Additionally, the tibiasize gauge 750 also includes features that serve to appropriatelyalign/orient the resection cuts on the proximal tibia 12, which in turnresults in proper alignment of the baseplate implant I on the resectedproximal tibia 12 to thereby minimize underhang/overhang of thebaseplate implant I on the resected proximal tibia 12. As should beappreciated, minimizing underhang/overhang of the baseplate implant I onthe resected proximal tibia 12 tends to provide a stronger and moresecure and stable engagement of the tibial implant on the proximal tibia12.

As shown in FIG. 43, the tibia size gauge 750 is used in associationwith an eminence stylus 300″ (which is a modified version of theeminence stylus 300) attached to the datum block 100, with the datumblock 100 in turn pinned to the proximal tibia 12, the details of whichhave been illustrated and described above. In the illustratedembodiment, the tibia size gauge 750 generally includes the eminencestylus 300″ which defines a scaled datum plate 760, and an indicatormember 770 removably attached to the scaled datum plate 760. Theindicator member 770 includes structures and features thatreference/engage medial and anterior aspects of the proximal tibia 12and, in cooperation with the scaled datum plate 760, provide a visualmeasurement indication as to the estimated/appropriate size of thetibial baseplate implant I to be installed on the proximal tibia 12subsequent to resection.

As indicated above, the eminence stylus 300″ is a modified version ofthe eminence stylus 300 illustrated and described above, and isconfigured virtually identical to the eminence stylus 300 with theexception of defining a scaled datum plate 760. More specifically, theeminence stylus 300″ generally includes a base portion or body 302″configured for attachment to the datum block 100, a carriage 304″movably attached to the base portion 302″ and configured for lineardisplacement along a longitudinal displacement axis L arranged in agenerally anterior-posterior direction, and a pair of articulating armsor indicator members 306 a″, 306 b″ pivotally attached to the carriage304″ and configured for pivotal displacement relative to the carriage304″. Additionally, the base portion 302″ generally includes a baseplate 310″, an inferior mounting flange 314″ extending from the baseplate 310″ in a medial-lateral direction, and a superior cutting guideflange 316″ extending from the base plate 310″ in a medial-lateraldirection and superiorly offset from the inferior mounting flange 314″.The mounting flange 314″ may be compressed against an inferior surfaceof the reference bench 104 via actuation of the pinch force mechanism106 to lock the eminence stylus 300″ in a select position andorientation relative to the datum block 100. Additionally, asubstantially flat/planar inferior surface defined by the cutting guideflange 316″ cooperates with a substantially flat/planar superior surfacedefined by the reference table 104 of the datum block 100 to therebyform a medial cutting guide or channel 348″ therebetween. It should beunderstood that the eminence stylus 300″ is configured substantiallyidentical to the eminence stylus 300 and operates in a mannersubstantially identical to that of the eminence stylus 300, with theexception of incorporation of the features associated with the scaleddatum plate 760 onto the superior surface 344″ of the cutting guideflange 316″.

As illustrated most clearly in FIGS. 45A and 45B, the scaled datum plate760 includes a measurement scale 762 that includes scaled measurementindicia 764 which serve to provide a visual indication as to thedistances being measured by the tibia size gauge 750. In the illustratedembodiment, the scaled measurement indicia 764 include a series ofparallel grooves 764 a cut into the superior surface 344″ of the cuttingguide flange 316″ and extending in an anterior-posterior direction, andnumbers 764 b corresponding to the grooves 764 a. In one embodiment, thegrooves 764 a are V-shaped and extend across the superior surface 344″in an anterior-posterior direction. Although one particular embodimentof the scaled measurement indicia 764 has been illustrated and describedherein, it should be understood that other suitable types andconfigurations of measurement indicia are also contemplated for use inassociation with the tibia size gauge 750.

In the illustrated embodiment, the indicator member 770 extends along alongitudinal axis L and generally includes an inferior flat/planar plate772 having a generally uniform and relatively thin plate thickness t(FIG. 44A), and a superior flat/planar plate 774 offset from theinferior plate 772 to define a gap G therebetween. The superior plate774 includes a tooth or projection 776 (FIG. 45A) extending into the gapG toward the inferior plate 772 and configured for sliding engagementwithin and along individual ones of the parallel grooves 764 a cut intothe superior surface 344″ of the cutting guide flange 316″. In theillustrated embodiment, the tooth 776 has a V-shaped profile and issized and shaped for sliding displacement along individual ones of theparallel V-shaped grooves 764 a (FIG. 45A). However, other suitableshapes and configurations of the tooth 776 and the grooves 764 a arealso contemplated. Additionally, the superior plate 774 is provided witha generally triangular-shaped outer profile defining an apex orarrowhead 778 at a distal end thereof. However, other suitable shapesand configurations of the superior plate 774 are also contemplated. Theindicator member 770 further includes a first reference arm 780extending axially from the inferior plate 772 and including a distalpointer 782 defining a distal end surface 784 configured for engagementwith a medial aspect of the proximal tibia 12, and a second referencearm 790 which also extends axially from the inferior plate 772 andincluding a distal pointer 792 defining a distal end surface 794configured for engagement with an anterior aspect of the proximal tibia12. In the illustrated embodiment, the distal end surfaces 784, 794 ofthe distal pointers 782, 792 are curved or rounded to provide secure andstable engagement with the medial and anterior outer surfaces of theproximal tibia 12. However, in other embodiments, the distal endsurfaces 784, 794 may be provided with a pointed configuration or ablunt configuration.

As shown in FIG. 43, the indictor member 770 is attached to the scaleddatum plate 760 (which corresponds to the cutting guide flange 316″ ofthe datum block 300″) by positioning the inferior plate 772 into themedial cutting guide 348″ (formed between the cutting guide flange 316″and the reference bench 104 of the datum block 100), and by positioningthe V-shaped tooth 776 defined by the superior plate 774 into one of theV-shaped grooves 764 a defined along the scaled datum plate 760. Asshould be appreciated, the superior-inferior location of the medialcutting guide 348″ determines the level/location of the resection cuts,and the inward-outward angular orientation of the eminence stylus 300″dictates the inward-outward angular orientation of the medial cuttingguide 348″ and the resulting orientation of the vertical eminenceresection cut.

Referring now to FIGS. 45A and 45B, shown there is a technique accordingto one form of the invention for using the tibia size gauge 750 toreference medial aspects of the proximal tibia 12 along the tibialcortex (e.g., at the medial tibial cortex 12 _(MC)) at theproposed/intended level of the horizontal resection cuts to determinethe appropriate position and orientation (i.e., angular alignment) ofthe resection cuts to be formed in the proximal tibia 12 to receive thetibial baseplate implant I. As indicated above, the datum block 100 isinitially pinned to the proximal tibia 12. Based on an initialestimation of the size of the tibial baseplate implant I to be installedon the proximal tibia 12, the indictor member 770 is attached to thescaled datum plate 760 by sliding the V-shaped tooth 776 of theindicator member 770 into the appropriate V-shaped groove 764 a on thescaled datum plate 760, and with the distal apex or arrowhead 778 of theindicator member 770 pointing to the estimated size of the tibialbaseplate implant I. As shown in the exemplary embodiment illustrated inFIG. 45B, the estimated size of the tibial baseplate implant I to beinstalled on the proximal tibia 12 is set to a size of “3”.

With the indictor member 770 fully engaged/assembly on the scaled datumplate 760 of the eminence stylus 300″, the eminence stylus 300″ (withthe indicator member 770 attached to the scaled datum plate 760 at thescale location corresponding to the estimated size of the implant I) isengaged to the reference bench 104 of the datum block 100 and isdisplaced in an anterior-posterior direction until the distal endsurface 784 of the pointer 782 is positioned in contact with the medialtibial cortex 12 _(MC), and the distal end surface 794 of the pointer792 associated with the second reference arm 790 is positioned incontact with the anterior tibial cortex 12 _(AC) of the proximal tibia12. Notably, these two points of contact between the indicator member770 and the proximal tibia 12 at the level of resection serve toeffectively center and align the eminence stylus 300″ relative to theproximal tibia 12 or other anatomic structures (e.g. cruciateligaments). Proper centering/alignment of the eminence stylus 300″ maybe checked/verified by observing the position/orientation of theindicator members 306 a″, 306 b″ relative to the proximal tibia 12 orother anatomic structures (e.g. cruciate ligaments). Although theillustrated embodiment establishes two points of contact between thetibia size gauge 750 and the proximal tibia 12, it should be understoodthat three or more points of contact between the tibia size gauge 750and the proximal tibia 12 may alternatively be established.

Once the eminence stylus 300″ (with the indictor member 770 attachedthereto and positioned in contact with the medial and anterior aspectsof the proximal tibia 12) is appropriately centered/aligned in relationto the proximal tibia 12, the eminence stylus 300″ may be locked inposition on the datum block 100 via actuation of the pinch lockmechanism 106. At this point, the indictor member 770 may be removedfrom the eminence stylus 300″. Because proper centering/alignment of theeminence stylus 300″ relative to the proximal tibia 12 using theabove-described centering/alignment technique results in formation ofthe resection cuts at the appropriate position and orientation, thetibial baseplate implant I will also be properly positioned/oriented onthe resected proximal tibia 12, whereby underhang/overhang of thebaseplate implant I is thereby minimized relative to the peripheralouter boundary of the proximal tibia 12.

As should be appreciated, the above-described technique forcentering/aligning the eminence stylus 300″ relative to the proximaltibia 12 utilizes an initial estimation of the size of the tibialimplant I to set the indictor member 770 at the appropriatelocation/position on the scaled datum plate 760, and then displaces theeminence stylus 300″ (with the indictor member 770 engaged thereto) inan anterior-posterior direction to establish at least two points ofcontact with the proximal tibia 12 at the level of proposed/intendedresection to center/align the eminence stylus 300″ relative to theproximal tibia 12, the accuracy of which can be confirmed/verified viathe indicator members 306 a″, 306 b″. However, other techniques forcentering/aligning the eminence stylus 300″ relative to the proximaltibia 12 using the tibia size gauge 750, as well as other uses of thetibia size gauge 750, are also contemplated.

For example, in another form of the invention, the datum block 100 isinitially pinned to the proximal tibia 12, and the eminence stylus 300″is provisionally engaged to the datum block 100 and generallycentered/aligned in relation to the proximal tibia 12 or other anatomicstructures using the indicator members 306 a″, 306 b″, the alignment rod18 and/or other alignment structures or alignment techniques. Once theeminence stylus 300″ is generally centered/aligned in relation to theproximal tibia 12, the eminence stylus 300″ may be provisionally lockedin position on the datum block 100 via partial actuation of the pinchlock mechanism 106 (i.e., movement of the eminence stylus 300″ isresisted but not prevented). The distal end surface 784 of the pointer782 is then be generally aligned with the medial tibial cortex 12 _(MC)on the medial side of the proximal tibia 12, and the V-shaped tooth 776defined by the superior plate 774 of the indicator member 770 ispositioned in the appropriate V-shaped groove 764 a defined along thescaled datum plate 760. The V-shaped tooth 776 is then displaced alongthe V-shaped groove 764 a by correspondingly displacing the indicatormember 770 in an anterior-posterior direction until the distal endsurface 784 of the pointer 782 is positioned in contact with the medialtibial cortex 12 _(MC), and the distal end surface 794 of the pointer792 associated with the second reference arm 790 is positioned incontact with the anterior tibial cortex 12 _(AC) of the proximal tibia12. If the distal end surface 784 of the pointer 782 does not contactthe medial tibial cortex 12 _(MC), the indicator member 770 isdisengaged from the scaled datum plate 760 and repositioned on thescaled datum plate 760 with the V-shaped tooth 776 positioned in adifferent V-shaped groove 764 a that provides contact of the distal endsurface 784 of the pointer 782 with the medial tibial cortex 12 _(MC),and contact of the distal end surface 794 of the pointer 792 with theanterior tibial cortex 12 _(AC). Notably, these two (or more) points ofcontact between the indicator member 770 and the proximal tibia 12further centers/aligns the eminence stylus 300″ to the appropriateposition/orientation relative to the proximal tibia 12. At this point,the eminence stylus 300″ may be fully locked in position on the datumblock 100 via full actuation of the pinch lock mechanism 106, followedby resection of the proximal tibia 12 using the techniques illustratedand described above.

Additionally, as shown in FIG. 45B, the user may observe which of thenumbers 764 b on the measurement scale 762 is aligned with the distalapex or arrowhead 778 defined by the indicator member 770. In theillustrated embodiment, the number 764 b aligned with the distal apex orarrowhead 778 relates to the size of the tibial baseplate implant I thatwould properly fit on the proximal tibia 12 subsequent to resection. Asshown in FIG. 45B, the indicated size measurement is “3”, whichcorresponds to the appropriate size of the tibial baseplate implant I tobe installed on the proximal tibia 12. Subsequent to resection andfinishing of the proximal tibia 12, the appropriately sized baseplateimplant I is installed on the resected proximal tibia 12 whereinunderhang/overhang of the baseplate implant I on the resected proximaltibia 12 is minimized relative to the peripheral outer boundary of theproximal tibia 12 due to the above-described implant sizing andalignment techniques.

I. Tibia Rotation Gauge

Referring to FIG. 46, shown therein is a tibia rotation gauge 800according to one form of the present invention. The tibia rotation gauge800 may be used to align/orient the eminence stylus 300 to theappropriate angular orientation relative to the proximal tibia 12, whichin turn aligns/orients the resection cuts on the proximal tibia 12 toensure proper alignment of the baseplate implant I on the resectedproximal tibia 12 to thereby minimize underhang/overhang of thebaseplate implant I on the resected proximal tibia 12. As should beappreciated, minimizing underhang/overhang of the baseplate implant I onthe resected proximal tibia 12 tends to provide a stronger and moresecure and stable engagement of the tibial implant on the proximal tibia12. As will be discussed in greater detail below, the tibia rotationgauge 800 is engaged with the eminence stylus 300 and includes alignmentfeatures that engage anterior aspects of the proximal tibia 12 to adjustthe angular position of the eminence stylus 300 to the appropriateorientation relative to the proximal tibia 12.

As shown in FIGS. 47A, 47B and 48, the tibia rotation gauge 800 may beused in association with the eminence stylus 300 attached to the datumblock 100, with the datum block 100 in turn pinned to the proximal tibia12, the details of which have been illustrated and described above.However, it should be understood that the tibia rotation gauge 800 mayalso be used in association other devices and instruments, including butnot limited to the eminence stylus 300′, the recut block 600, the tibiasize gauge 700, and the tibia size gauge 750. The tibia rotation gauge800 may be particularly useful when used in association with the tibiasize gauge 700 and/or the tibia size gauge 750 to align/orient theeminence stylus 300 to the appropriate orientation relative to theproximal tibia 12 prior to performing the sizing/centering techniquesassociated with the tibia size gauge 700 and the sizing/alignmenttechniques associated with the tibia size gauge 750.

Referring once again to FIG. 46, in the illustrated embodiment, thetibia rotation gauge 800 extends along a longitudinal axis L andgenerally includes a base plate or handle portion 802, a medialalignment leg 804 a extending axially from the base plate 802 andincluding a distal alignment foot or flange 806 a defining a distal endbone-contacting surface or edge 808 a configured for engagement with theanterior outer surface of the proximal tibia 12, and a lateral alignmentleg 804 b extending axially from the base plate 802 and including adistal alignment foot or flange 806 b defining a distal endbone-contacting surface or edge 808 b configured for engagement with theanterior outer surface of the proximal tibia 12. The distal endbone-contacting surfaces or edges 808 a, 808 b are outwardly tapered ata taper angle θ relative to the longitudinal axis L. The taper angle θis preferably set to generally match or conform to the contour or outerprofile of the anterior outer surface of the proximal tibia 12, and morespecifically the anterior tibial cortex 12 _(AC), at the level of thehorizontal resection cuts. In one embodiment, the taper angle θ fallswithin a range of about 30° to 90°. In another embodiment, the taperangle θ falls within a range of about 45° to 75°. In a furtherembodiment, the taper angle θ is set at approximately 60°. However,other taper angles θ are also contemplated. Additionally, in theillustrated embodiment, the distal end surfaces or edges 808 a, 808 bare substantially flat/planar. However, in other embodiments, the distalend surfaces or edges 808 a, 808 b may be curved or partially curved ina concave or convex configuration.

The tibia rotation gauge 800 further defines a slot or open inner region810 arranged generally along the longitudinal axis L and extending froman open end adjacent the distal end surfaces or edges 808 a, 808 btoward the base plate 802. The open ended slot 810 has a generallyrectangular configuration and is bound/defined by the distal endsurfaces or edges 808 a, 808 b, substantially flat/planar inner sidesurfaces or edges 805 a, 805 b defined by the medial and lateralalignment legs 804 a, 804 and arranged generally parallel with thelongitudinal axis L, and a substantially flat/planar inner end surface803 defined by the base plate 802 and arranged generally perpendicularto the longitudinal axis L. As will be discussed below, the open endedslot 810 is sized to receive the base plate 310 defined by the main body302 of the eminence stylus 300 (FIGS. 17-20) therein such that theplanar inner side surfaces or edges 805 a, 805 b of the medial andlateral alignment legs 804 a, 804 b are engaged in relatively closetolerance with the substantially flat/planar outer side surface of thebase plate 310.

Additionally, in the illustrated embodiment, the tibia rotation gauge800 is provided as a single-piece, substantially flat/planar platehaving a generally uniform and relatively thin plate thickness that ispreferably sized in relatively close tolerance with the width of themedial cutting guide 348 defined between the datum block 100 and theeminence stylus 300. However, other embodiments are also contemplatedwherein the tibia rotation gauge 800 may take on other configurationsand/or may be provided as multiple pieces or elements that areinterconnected with one another to form the tibia rotation gauge 800.

Referring now to FIGS. 47-49, shown there is a technique according toone form of the invention for using the tibia rotation gauge 800 toalign/orient the eminence stylus 300 to the appropriate angularorientation relative to the proximal tibia 12, which in turnaligns/orients the resection cuts on the proximal tibia 12 to ensureproper alignment of the baseplate implant I on the resected proximaltibia 12 to minimize underhang/overhang of the baseplate implant I onthe resected proximal tibia 12.

Referring to FIGS. 47A and 47B, the datum block 100 is initially pinnedto the proximal tibia 12, and the eminence stylus 300 is engaged to thedatum block 100 and generally centered/aligned in relation to theproximal tibia 12 or other anatomic structures using the indicatormembers 306 a, 306 b, the alignment rod 18 and/or other alignmentstructures or alignment techniques. Once the eminence stylus 300 iscentered/aligned in relation to the proximal tibia 12, the eminencestylus 300 may be locked in position on the datum block 100 viaactuation of the pinch lock mechanism 106. However, as shown in FIGS.47A and 47B, in some instances, the eminence stylus 300 may remain in amisaligned angular orientation relative to the proximal tibia 12. Inother words, the central plane P of the eminence stylus 300 (definedbetween the flat/planar indicator members 306 a, 306 b) may not beproperly aligned with the central anatomic plane P_(T) of the tibia(i.e., the central plane P of the eminence stylus 300 isinwardly/outwardly rotational offset from the central anatomic planeP_(T) of the tibia).

Referring to FIGS. 48 and 49, the misaligned condition of the eminencestylus 300 (FIGS. 47A and 47B) may be corrected via use of the tibiarotation gauge 800. First, the eminence stylus 300 is unlocked from thedatum block 100 via de-actuation of the pinch lock mechanism 106 suchthat the eminence stylus 300 is free to internally/externally rotaterelative to the datum block 100. The tibia rotation gauge 800 is thenengaged to the eminence stylus 300 by aligning the open ended slot 810of the tibia rotation gauge 800 with the base plate 310 of the eminencestylus 300 and inserting the medial alignment leg 804 a into the medialcutting guide 348 (defined between the cutting guide flange 316 on theeminence stylus 300 and the reference bench 104 on the datum block 100).As discussed above in association with FIGS. 20A-20C, the medial cuttingguide 348 is used to form the medial horizontal resection cut C_(HM) inthe proximal tibia 12, and the cutting plane defined along the medialcutting guide 348 is therefore positioned at the level of resection. Thethickness of at least the medial alignment leg 804 a is preferably sizedin relatively close tolerance with the width of the medial cutting guide348 to maintain the tibia rotation gauge 800 in a substantiallyco-planar relationship with the cutting plane defined by the medialcutting guide 348.

As should be appreciated, the planar inner side surfaces or edges 805 a,805 b defined by the medial and lateral alignment legs 804 a, 804 b ofthe tibia rotation gauge 800 are engaged in relatively close tolerancewith the substantially flat/planar outer side surface of the base plate310 of the eminence stylus 300. Accordingly, angular rotation of thetibia rotation gauge 800 will result in corresponding angular rotationof the eminence stylus 300. As the tibia rotation gauge 800 is displacedalong the base plate 310 of the eminence stylus 300 in ananterior-posterior direction (in the direction of arrow A), the distalfeet 806 a, 806 b of the medial and lateral alignment legs 804 a, 804 bwill engage the anterior surface of the proximal tibia 12 at the levelof resection (i.e., at the level where the horizontal resection cutswill be formed). More specifically, the distal bone-contacting surfacesor edges 808 a, 808 b defined by the distal feet 806 a, 806 b willengage the anterior tibial cortex 12 _(AC) to define at least two pointsor locations of contact between the tibia rotation gauge 800 and theanterior surface of the proximal tibia 12 at the level of resection. Asindicated above, the distal bone-contacting surfaces or edges 808 a, 808b are configured to generally match or conform to the profile of theanterior outer surface of the proximal tibia 12 at the level ofresection. Accordingly, as the tibia rotation gauge 800 is displaced inthe direction of arrow A and into compressed engagement with theproximal tibia 12, engagement of the distal bone-contacting surfaces oredges 808 a, 808 b against the anterior tibial cortex 12 _(AC) along twoestablished points or locations of contact will draw the tibia rotationgauge 800 into proper alignment with the proximal tibia 12, which willin turn rotate the eminence stylus 300 into a properly alignedorientation relative to the proximal tibia 12 with the central plane Pof the eminence stylus 300 generally aligned with the central anatomicplane P_(T) of the tibia. At this point, the eminence stylus 300 mayonce again be locked in position on the datum block 100 via actuation ofthe pinch lock mechanism 106, and the tibia rotation gauge 800 can beremoved from the eminence stylus 300.

As should be appreciated, use of the tibia rotation gauge 800 toproperly align the eminence stylus 300 to the correct angularorientation relative to the proximal tibia 12 will result in formationof the resection cuts at the proper alignment and orientation relativeto the proximal tibia 12, which will in turn ensure proper alignment ofthe baseplate implant I on the resected proximal tibia 12 to minimizeunderhang/overhang of the baseplate implant I relative to the outerperiphery of the resected proximal tibia 12. As should also beappreciated, minimizing underhang/overhang of the baseplate implant I onthe resected proximal tibia 12 tends to provide a stronger and moresecure and stable engagement of the tibial implant on the proximal tibia12. Additionally, it should be further appreciated that the tibiarotation guide 800 is ambidextrous, meaning that the tibia rotationguide 800 can be used to perform knee arthroplasty procedures on boththe right knee and the left knee.

Referring to FIG. 50, the points of contact between the tibia rotationguide 800 and the baseplate implant I are substantially similar to thepoints of contact between the tibia rotation guide 800 and the anteriorsurface of the proximal tibia 12 at the level of resection. Accordingly,use of the tibia rotation gauge 800 to properly align the eminencestylus 300 relative to the proximal tibia 12 prior to forming theresection cuts will ensure a properly aligned fit of the baseplateimplant I on the resected proximal tibia 12. As shown in FIG. 51, sincethe shape and configuration of the distal feet 806 a, 806 b of the tibiarotation gauge 800 are compatible with multiple sizes of the baseplateimplant I (shown in phantom), the same tibia rotation gauge 800 may beused universally across the multiple sizes of the baseplate implants I(i.e., a different tibia rotation gauge 800 is not required toaccommodate various sizes of the baseplate implant I).

J. Tibia Insert Trial

Referring to FIG. 52, shown therein is a tibia insert trial 900according to one form of the present invention. As will be discussed ingreater detail below, the tibia insert trial 900 is used in theevaluation of the medial tibial resection R_(M) (FIGS. 55A and 56A) tocheck/verify the size, shape, depth, position and/or orientation of thecuts associated with the medial tibial resection R_(M) and theirrelation to the femoral trial 18 attached to the distal femur 10, and/orin the simultaneous evaluation of the medial and lateral tibialresections R_(M), R_(L) (FIGS. 55B and 56B) to check/verify the size,shape, depth, position and/or orientation of the cuts associated withthe medial and lateral tibial resection R_(M), R_(L) and their relationto the femoral trial 18 attached to the distal femur 10.

Evaluations using the tibia insert trial 900 can take the form of avariety of different checks on the suitability of the size, shape,depth, position and/or orientation of the medial resection R_(M) or themedial and lateral resections R_(M), R_(L), or the potential need tore-cut or redo the resection cuts at a different depth or orientation(e.g., at a different posterior slope angle, at a different varus-valgusangle, and/or at an inward-outward rotation angle). In some embodiments,evaluations using the tibia insert trial 900 can take the form ofarticulating a femoral trial (FIG. 56A) on a medial lobe of the tibiainsert trial 900, which may allow the surgeon to check the balance,tightness, and/or laxity of the knee joint in flexion and extension. Inother embodiments, evaluations using the tibia insert trial 900 can takethe form of simultaneously articulating a femoral trial (FIG. 56B) onmedial and lateral lobes of the tibia insert trial 900, which may alsoallow the surgeon to check the balance, tightness, and/or laxity of theknee joint in flexion and extension. In still other embodiments,evaluations using the tibia insert trial 900 can involve the selectionof one or more shim components (selected from a kit or set of shimcomponents) that are removably attachable to a main trial component toprovide various configurations of trial lobes (i.e., varyingthicknesses, posterior slope angles, varus-valgus angles, etc.) toevaluate the relationship between the medial/lateral resections of theproximal tibia and a femoral trial attached to the distal femur 10. Instill further embodiments, the tibia insert trial 900 may also be usedto simulate the effect of a re-cut of the medial/lateral resections orthe use of a different tibial implant articulation on the balance of theknee joint which may, in some embodiments, reduce the risk associatedwith having to re-cut the resection.

Referring collectively to FIGS. 52 and 53, in the illustratedembodiment, the tibia insert trial 900 is configured as a two-pieceassembly including a main trial component 902 and a shim component 904that are removably attachable to one another to form the tibia inserttrial 900. In one embodiment, the main trial component 902 and the shimcomponent 904 each have substantially identical outer cross-sectionalshapes/profiles that substantially match up with another when assembledtogether. In another embodiment, the shim component 904 is removablyattachable to the main trial component 902 by way of one or moremagnetic attraction forces. As shown in FIG. 54, the inferior side ofthe main trial component 902 is provided with a series of magnets 906projecting therefrom that are received in corresponding openings 908formed in the shim component 904 (FIG. 53). As should be appreciated, atleast the portion of the shim component 904 surrounding the openings 908may be formed of a ferrous material to generate a magnetic attractionforce with the magnets 906 to maintain a connection between the maintrial component 902 and the shim component 904. Positioning of themagnets 906 within the openings 908 not only serves to draw the maintrial component 902 and the shim component 904 into connection with oneanother via magnetic attraction forces, but also serves as a positiveinterconnection or catch that prevents the components from sliding offof one another. Although the shim component 904 has been illustrated anddescribed as being removably attachable to the main body component 902by way of one or more magnetic attraction forces, other structures andtechniques may alternatively be used to removably attach the shimcomponent 904 to the main body component 902 including, for example, afriction fit, a clamp fit, a tongue-and-groove arrangement, one or morefasteners, or by other suitable structures or techniques for removableattachment of the shim component 904 to the main body component 902.

In the illustrated embodiment, the magnets 906 and the openings 908 havebeen illustrated as having a circular configuration. However, othersuitable shapes and configurations of the magnets 906 and the openings908 are also contemplated. Additionally, although the magnets 906 havebeen illustrated as being associated with the main trial component 902and the openings 908 have been illustrated as being associated with theshim component 904, it should be understood that a reverse configurationis also contemplated. Further, in the illustrated embodiment, themagnets 906 project from a surface of the main trial component 902 forreceipt within corresponding openings 908 in the shim component 904.However, in other embodiments, the magnets 906 may be embedded withinportions of either the main trial component 902 or the shim component904. Moreover, although the magnets 906 have been illustrated asextending from each of the three lobed regions of the main trialcomponent 902 and the openings 908 have been illustrated as beingdefined in each of the three lobed regions of the shim component 904, itshould be understood that the magnets 906 and the openings 908 canalternatively be associated with other portions/regions of the maintrial component 902 and the shim component 904 such as, for example, theinterconnecting handle 910. Additionally, although the main trialcomponent 902 has been illustrated as including three magnets, it shouldalso be understood that any number of the magnets 906 positionablewithin a corresponding number of openings 908 may be used to removablyattach the shim component 904 to the main trial component 902.

As discussed above, in the illustrated embodiment, the main trialcomponent 902 and the shim component 904 each have substantiallyidentical outer cross-sectional shapes/profiles that substantially matchup with another when assembled together. However, the main trialcomponent 902 and the shim component 904 may be provided with one ormore outer profile regions that do not correspond to one another tofacilitate separation of the components. For example, in one embodiment,the shim component 904 is provided with a cut-out or recessed region 904a (FIGS. 53 and 56B) that is not found in the corresponding area of themain trial component 902, thereby allowing the user to more easily graspand manipulate the main trial component 902 relative to the shimcomponent 904 to facilitate separation of the components. Additionally,the shim component 904 may be provided with a projecting region orflange 904 b (FIGS. 53 and 56A) that is not found in the correspondingarea of the main trial component 902, thereby allowing the user to moreeasily grasp and manipulate the shim component 904 relative to the maintrial component 902 to facilitate separation of the components. Itshould be understood that other features associated with the main trialcomponent 902 and/or the shim component 904 may be provided thatfacilitate separation of the components from one another. Additionally,in still other embodiments, multiple shim components may be providedthat are removably attached to just the lobed regions of the main bodycomponent 902, or multiple trial components may be provided that areremovably attached to just the lobed regions of the shim component.Moreover, although the tibia insert trial 900 has been illustrated anddescribed as a two-piece assembly including a main trial component 902removably attached to a shim component 904, other embodiments are alsocontemplated wherein the tibia insert trial 900 comprises a unitary,single-piece structure.

Referring collectively to FIGS. 52-54, in the illustrated embodiment,the tibia insert trial 900 includes an elongate connector portion orhandle 910, a single-lobe trial portion 912 located at a first end ofthe handle 910 and including a medial tibia trial lobe 912 a, and adual-lobe trial portion 914 located at an opposite second end of thehandle 910 and including both a medial tibia trial lobe 914 a and alateral tibia trial lobe 914 b. The medial tibia trial lobes 912 a, 914a each have a hemi-elliptical or hemi-ovular configuration sized andshaped to generally match the size and shape of the corresponding medialportion of the tibia implant to be installed on the proximal tibia 12.Similarly, the lateral tibia trial lobe 914 b has a hemi-elliptical orhemi-ovular configuration sized and shaped to generally match the sizeand shape of the corresponding lateral portion of the tibia implant tobe installed on the proximal tibia 12. Accordingly, the tibia inserttrial 900 can be used to evaluate/check the suitability of the size andshape of the medial resection R_(M) or the medial and lateral resectionsR_(M), R_(L) and whether the resections will accommodate the tibialimplant to be installed on the proximal tibia 12. Additionally, each ofthe tibia trial lobes 912 a, 914 a and 914 b includes a substantiallyflat/planar inferior surface 916 (defined by the shim component 904)that is configured to rest against/abut the superior horizontal surfacesof the medial and lateral resections R_(M), R_(L) of the proximal tibia12. Each of the tibia trial lobes 912 a, 914 a and 914 b also includes asuperior articulation surface 918 (defined by the main trial component902) that is curved/contoured to match a particular implant and to matewith the corresponding curved/contoured inferior surface defined by thefemoral trial 18 attached to the distal femur 10.

In the illustrated embodiment, the dual-lobe trial portion 914 includesan open ended slot or spacing 920 which separates the medial and lateraltibia trial lobes 914 a, 914 b and which has a width w_(S) slightlylarger greater than the width w_(T) of the tibial eminence 14 (FIG. 55B)so as to allow the medial and lateral tibia trial lobes 914 a, 914 b tobe simultaneous positioned on the medial and lateral resections R_(M),R_(L), and with the tibial eminence 14 positioned within the open endedslot 920 (FIG. 56B). Additionally, in some embodiments, the dual-lobetrial portion 914 is used to evaluate the medial and lateral resectionR_(M), R_(L) prior to resection of the anterior tibial eminence 14 _(A)(discussed below). Thus, the overall length l_(S) of the slot 920 mustbe sized to accommodate the full anterior-posterior length of the tibialeminence 14 prior to anterior resection of the tibial eminence 14.Accordingly, the slot 920 is provided with an extended portion 920 athat extends beyond the anterior ends of the medial and lateral tibiatrial lobes 914 a, 914 b adjacent the handle portion 910 for receipt ofthe unresected anterior tibial eminence 14 _(A). Stated another way, thehandle portion 910 includes a notched bridge region 910 a thatinterconnects the medial and lateral tibia trial lobes 914 a, 914 b andwhich is sized to receive the unresected anterior tibial eminence 14_(A) therein.

As should be appreciated, the medial tibia trial lobe 912 a of thesingle-lobe trial portion 912 is configured for positioning on themedial resection R_(M) (FIGS. 55A and 56A) for evaluation of the size,shape, depth, position and/or orientation of the medial resection R_(M)and their relation to the femoral trial 18 attached to the distal femur10. As should also be appreciated, the medial and lateral tibia triallobe 914 a, 914 b of the dual-lobe trial portion 914 are configured forsimultaneous positioning on the medial and lateral resections R_(M),R_(L) (FIGS. 55B and 56B) for simultaneous evaluation of the size,shape, depth, position and/or orientation of the medial and lateraltibial resections R_(M), R_(L) and their relation to the femoral trial18 attached to the distal femur 10. As should be further appreciated,due to the unique configuration of the tibia insert trial 900, each ofthese evaluations can be performed using a single instrument as opposedto two separate instruments. Additionally, although not specificallyillustrated in FIGS. 52-54, it should be understood that in analternative embodiment, another single-lobe trial portion may extendfrom a central portion of the handle 910 which includes a single lateraltibia trial lobe configured for positioning on the lateral resectionR_(L) for evaluation of the size, shape, depth, position and/ororientation of the lateral resection R_(L) and their relation to thefemoral trial 18.

In another form of the present invention, the tibia insert trial 900 mayprovided in a kit or set including multiple main trial components 902and multiple shim components 904. The main trial components 902 may beprovided in various sizes/articulation configurations that correspond tothe various sizes/articulation configurations associated with the tibialimplants that may be installed on the proximal tibia 12. The shimcomponents 904 may be provided in various sizes that correspond to thesizes of the main trial components 902, and in various incrementalthicknesses (i.e., +1, +2, +3, etc.) that serve to vary the overallthickness of the tibia trial lobes 912 a, 914 a and 914 b to simulatethe thickness of the tibial implant to be installed on the proximaltibia 12, and to check/verify whether the depth of the medial resectionR_(M) or the medial and lateral resections R_(M), R_(L) arecorrect/appropriate or if a re-cut is necessary. Additionally, a shimcomponent 904 having a particular thicknesses may be selected andattached to the main trial component 902 to simulate the effect of are-cut (i.e., a “re-cut simulation” to simulate a different resectioncut depth) to check/verify whether the proposed re-cut is desired priorto actually making the re-cut. In this way, the surgeon may investigateoptions for compensating for laxity or tightness in flexion/extensionwithout actually performing the proposed re-cut. As should beappreciated, the number of potential re-cuts is therefore minimized.

In addition to providing the shim components 904 in various incrementalthicknesses, the insert trial kit/set may also be provided with shimcomponents 904 having various incremental posterior slope angles (i.e.,−2, −1, 0, +1, +2, etc.) that serve to vary the posterior slope angleassociated with the tibia trial lobes 912 a, 914 a and 914 b to simulatethe posterior slope angle of the tibial implant to be installed onto theproximal tibia 12, and to check/verify whether the medial resectionR_(M) or the medial and lateral resections R_(M), R_(L) arecorrect/appropriate or whether a re-cut is necessary. Additionally, theinsert trial kit/set may also be provided with shim components 904having various incremental varus/valgus angles (i.e., −2, −1, 0, +1, +2,etc.) that serve to vary the varus/valgus angles associated with thetibia trial lobes 912 a, 914 a and 914 b to simulate the varus/valgusangle of the tibial implant to be installed onto the proximal tibia 12,and to check/verify whether the medial resection R_(M) or the medial andlateral resections R_(M), R_(L) are correct/appropriate or whether are-cut is necessary. Accordingly, a shim component 904 having aparticular posterior slope angle and/or a particular varus/valgus anglemay be selected and attached to the main trial component 902 to simulatethe effect of a re-cut (i.e., a “re-cut simulation” to simulate adifferent posterior slope angle and/or a different varus/valgus angle)to check/verify whether the proposed re-cut is desired prior to actuallymaking the re-cut.

In other embodiments, multiple shim components 904 may be attached tothe main trial component 902 to vary both the overall thickness of thetibia trial lobes 912 a, 914 a and 914 b, and to vary the posteriorslope angle and/or the varus/valgus angle. For example, a first shimcomponent 904 a having a particular thicknesses may be selected andattached to the main trial component 902, and a second shim component904 b having a particular posterior slope angle and/or varus/valgusangle may be selected and attached to the first shim component 904 b. Asshould be appreciated, this additional degree of modularity may reducethe number of shim components 904 included in the kit/set associatedwith the tibia insert trial 900 (i.e., eliminating the need for shimcomponents 904 having varying posterior slope angles and/or varus/valgusangles in multiple thickness levels). As should also be appreciated,each of the shim components 904 is ambidextrous, meaning that the shimcomponent 904 can be flipped over and used in association with the otherknee. Accordingly, individual shim components 940 can be used to performknee arthroplasty procedures on both the right knee and the left knee.

K. Tibia Size Templates

Referring to FIGS. 57-60, shown therein is a tibia size template 1000according to one form of the present invention. Unlike the tibia inserttrial 900 illustrated and described above which is used to evaluate themedial resection R_(M) or the medial and lateral tibial resectionsR_(M), R_(L) in relation to a femoral trial 18 attached to the distalfemur 10 (i.e., to evaluate articulation, balance, tightness, and/orlaxity of the knee joint in flexion and extension), use of the tibiasize template 1000 is limited to evaluation of the peripheral size andshape of the medial resection R_(M) individually, or the medial andlateral tibial resections R_(M), R_(L) simultaneously. Accordingly, theprimary evaluation feature associated with the tibia size template 1000is the peripheral outer cross-sectional profile of the lobed regions.Due to the simple design associated with the tibia size template 1000,manufacturing costs may be significantly reduced compared to the tibiainsert trial 900.

The tibia size template 1000 is configured as a single-piece structureincluding an elongate connector portion or handle 1010, a single-lobetemplate portion 1012 located at a first end of the handle 1010 andincluding a medial tibia template lobe 1012 a, and a dual-lobe templateportion 1014 located at an opposite second end of the handle 1010 andincluding both a medial tibia template lobe 1014 a and a lateral tibiatemplate lobe 1014 b. The medial tibia template lobes 1012 a, 1014 aeach have a hemi-elliptical or hemi-ovular configuration sized andshaped to generally match the size and shape of the corresponding medialportion of the tibia implant to be installed on the medial resectionR_(M) of the proximal tibia 12. Similarly, the lateral tibia templatelobe 1014 b has a hemi-elliptical or hemi-ovular configuration sized andshaped to generally match the size and shape of the correspondinglateral portion of the tibia implant to be installed on the lateralresection R_(L) of the proximal tibia 12. Additionally, each of thetibia template lobes 1012 a, 1014 a and 1014 b includes a substantiallyflat/planar inferior surface 1016 and a substantially flat/planarsuperior surface 1018 (FIGS. 58A/58B and 59A/59B) so that the templatelobes rest steadily on the planar horizontal resected surfaces of themedial and lateral tibial resections R_(M), R_(L).

In a further embodiment, the inferior and superior surfaces 1016, 1018of the tibia size template 1000 each define reference marks or lines1016 a, 1018 a, respectively, along the mesial linear portion of each ofthe template lobes 1012 a, 1014 a and 1014 b. These reference marks 1016a, 1018 a are each located at the same offset position relative to theend of the handle 1010 (i.e., relative to the inward end of each of thelobes 1012 a, 1014 a and 1014 b). As shown in FIGS. 59B and 60B, thereference marks 1016 a, 1018 a are used as a template to form areference mark/line M vertically along the vertical medial and lateralresection cuts C_(VM), C_(VL) and across the superior surface of theanterior tibial eminence 14 _(A). These reference marks M serve as cutreference lines during removal of the anterior tibial eminence 14 _(A)using the anterior chisel 1100 illustrated and described below, andrepresent the ideal location of the vertical cut along the anteriortibial eminence 14 _(A). Although the reference marks M are illustratedas being formed using the dual-lobe template portion 1014 of the tibiasize template 1000, it should be understood that the reference marks Mcan also be made using the single-lobe template portion 1012.Additionally, the reference marks M can be formed on the surface of thebone by scribing, burning, or by any other suitable method for markingbone tissue. Further, each of the tibia template lobes 1012 a, 1014 aand 1014 b includes a hollow interior region 1019 (i.e., the templatelobes 1012 a, 1014 a and 1014 b are formed by relatively thin frame-likesections of material) to permit visualization through the template lobes1012 a, 1014 a and 1014 b when placed on the horizontal resectedsurfaces of the medial and lateral tibial resections R_(M), R_(L), toaid in identifying any misfit or misaligned regions.

The dual-lobe template portion 1014 includes a slot or spacing 1020separating the medial and lateral tibia template lobes 1014 a, 1014 bhaving a width w_(S) (FIG. 59A) that is slightly larger than the widthw_(T) (FIG. 59B) of the anterior tibial eminence 14 _(A) so as to allowthe medial and lateral tibia template lobes 1014 a, 1014 b to besimultaneous positioned on the medial and lateral tibial resectionsR_(M), R_(L), (FIGS. 59B and 60B). Additionally, in some embodiments,the dual-lobe template portion 1014 is used to evaluate the medial andlateral tibial resections R_(M), R_(L), prior to resection of theanterior tibial eminence 14 _(A) (discussed below). Thus, the overalllength l_(S) of the slot 1020 (FIG. 59A) must be sized to accommodatethe full anterior-posterior length of the tibial eminence 14 prior toprior to resection of the anterior tibial eminence 14 _(A). Accordingly,the slot 1020 includes an extended portion 1020 a that extends beyondthe anterior ends of the medial and lateral tibia template lobes 1014 a,1014 b adjacent the handle 1010 for receipt of the unresected anteriortibial eminence 14 _(A). Stated another way, the handle portion 1010includes a notched bridge region 1010 a that interconnects the medialand lateral tibia template lobes 1014 a, 1014 b and which is sized toreceive the unresected anterior tibial eminence 14 _(A) therein.

As should be appreciated, the medial tibia template lobe 1012 a of thesingle-lobe template portion 1012 is configured for positioning on themedial tibial resection R_(M) (FIGS. 59A and 60A) for evaluation of theperipheral size and shape of the medial tibial resection R_(M). Asshould also be appreciated, the medial and lateral tibia template lobes1014 a, 1014 b of the dual-lobe template portion 1014 are configured forsimultaneous positioning on the medial and lateral tibial resectionR_(M), R_(L) (FIGS. 59B and 60B) for simultaneous evaluation of theperipheral size and shape of the medial and lateral tibial resectionR_(M), R_(L). As should be further appreciated, due to the uniqueconfiguration of the tibia size template 1000, each of these evaluationscan be performed using a single instrument as opposed to two separateinstruments. It should also be appreciated that the tibia size template1000 is ambidextrous, meaning the tibia size template 1000 can beflipped over and used in association with the other knee. Accordingly, asingle tibia size template 1000 can be used to perform knee arthroplastyprocedures on both the right knee and the left knee. Additionally,although not specifically illustrated in FIGS. 57-60, it should beunderstood that in an alternative embodiment, another single-lobetemplate portion may extend from a central portion of the handle 1010which includes a lateral tibia template lobe configured for positioningon the lateral tibial resection R_(L) for evaluation of the peripheralsize and shape of the lateral tibial resection R_(L).

L. Anterior Chisel

Referring to FIGS. 61A and 61B, shown therein is an anterior chisel 1100according to one form of the present invention. As will be discussed ingreater detail below, the anterior chisel 1100 is designed andconfigured to form both vertical and horizontal cuts along the anteriorportion 14 _(A) of the tibial eminence 14 (FIGS. 64A and 64B) forresection/removal of the anterior tibial eminence portion 14 _(A) (FIG.64C) to provide sufficient clearance for receipt of a tibial implant.

In one embodiment, the anterior portion of the tibial eminence 14 _(A)is removed prior to forming keel slots/openings in the resected regionof the proximal tibia 12 using the keel formation instrument 1200illustrated and described below. It should be appreciated that priorremoval of the anterior tibial eminence 14 _(A) may make formation ofthe anterior keel slot somewhat easier (i.e., requiring less axialcutting force) because of not having to penetrate through the thicknessof the anterior tibial eminence 14 _(A). Additionally, removal of theanterior tibial eminence 14 _(A) prior to forming the keelslots/openings allows for the use of a tibial baseplate trial having ashape/profile that generally matches that of the tibial implant to beinstalled on the fully resected proximal tibia 12 to aid ingauging/trialing and/or formation of the keel slots/openings (FIGS. 68and 69). However, in other embodiments, the anterior tibial eminence 14_(A) may be removed subsequent to forming the keel slots/openings in theresected region of the proximal tibia 12.

In the illustrated embodiment, the anterior chisel 1100 generallyincludes a cutting block 1102 and an elongate shaft 1104 connected tothe cutting block 1102 and extending along a longitudinal axis L. Aproximal handle or gripping portion (not shown) may be attached to theproximal end of the elongate shaft 1104 to facilitate manipulation andhandling of the anterior chisel 1100 by the user, and to aid in theapplication of an axial cutting force F onto the elongate shaft 1104generally along the longitudinal axis L. The axial cutting force F istransmitted along the elongate shaft 1104 and is transferred to thecutting block 1102 to form the vertical and horizontal cuts along theanterior tibial eminence portion 14 _(A). The cutting block 1102includes a substantially flat/planar axially-facing end surface 1106that is arranged generally perpendicular to the longitudinal axis L.

In one embodiment, the cutting block 1102 is a single-piece monolithicblock defining a hollow interior surrounded by outer walls that define afirst slot 1110 sized and configured for receipt of a first cuttingblade 1112 extending along a first cutting plane arranged generallyparallel with the longitudinal axis L. The first cutting blade 1112 isattached to the cutting block 1102 via a fastener 1114 and includes adistal cutting edge 1116 positioned in general alignment with the planarend surface 1106 of the cutting block 1102 (FIGS. 63A/63B). The outerwalls of the cutting block 1102 further define a second slot 1120 sizedand configured for receipt of a second cutting blade 1122 extendingalong a second cutting plane arranged generally parallel with thelongitudinal axis L. The second cutting blade 1122 is attached to thecutting block 1102 via a fastener 1124 and includes a distal cuttingedge 1126 that is also positioned in general alignment with the planarend surface 1106 of the cutting block 1102. In the illustratedembodiment, the first cutting plane defined by the first cutting blade1112 extends substantially parallel with the second cutting planedefined by the second cutting blade 1122. However, other embodiments arealso contemplated wherein the first and second cutting planes are notarranged parallel with one another. As will be discussed in greaterdetail below, the first cutting blade 1112 is arranged to form thevertical cut C_(VA) along the anterior tibial eminence 14 _(A) (FIGS.62A, 63A and 64A), and the second cutting blade 1122 is arranged to formthe horizontal cut C_(HA) along the anterior tibial eminence 14 _(A)(FIGS. 62B, 63B and 64B).

In the illustrated embodiment, the anterior chisel 1100 also includesalignment and guide features that serve to properly align and guide thecutting blades 1112, 1122 relative to the proximal tibia 12 to form thevertical and horizontal cuts C_(VA), C_(HA) along the anterior tibialeminence 14 _(A). The anterior chisel 1100 further includes stopfeatures that limit the bone penetration depth of the vertical andhorizontal cuts C_(VA), C_(HA) to prevent the cutting blades 1112, 1122from cutting too deep into the anterior tibial eminence 14 _(A).

In one embodiment, the anterior chisel 1100 includes a pair of elongatelegs or axial projections 1130 a, 1130 b that extend from the cuttingblock 1102 in a direction substantially parallel with the longitudinalaxis L and which are positioned on opposite sides of the longitudinalaxis L. The axial projections 1130 a, 1130 b define substantiallyflat/planar surfaces 1132 along a first side that are arranged generallyco-planar with one another, and substantially flat/planar surfaces 1134along an opposite second side that are arranged co-planar with oneanother. The planar surfaces 1132 extend along a guide/alignment planearranged substantially parallel with and offset from the cutting planeof the first cutting blade 1112, and the planar surfaces 1134 extendalong a guide/alignment plane arranged substantially parallel andco-planar with the cutting plane of the second cutting blade 1122. Aswill be discussed below, the flat/planar surfaces 1132, 1134 serve toproperly align and guide the cutting blades 1112, 1122 relative to theproximal tibia 12 to form the vertical and horizontal cuts C_(VA),C_(HA) along the anterior tibial eminence 14 _(A). Although the axialprojections 1130 a, 1130 b have been illustrated and described as havinga particular configuration, it should be understood that otherstructures and means for aligning and guiding the anterior chisel 1100and the cutting blades 1112, 1122 relative to the proximal tibia 12 arealso contemplated including, for example, shoulder portions, flangeportions, plate portions, lip portions, step portions, or any otherstructure suitable to align and guide the anterior chisel 1100 and thecutting blades 1112, 1122 relative to the proximal tibia 12.

In another embodiment, the anterior chisel 1100 includes a pair of stopmembers or feet 1140 a, 1140 b that extend from the cutting block 1102in a direction substantially perpendicular to the longitudinal axis Land which are positioned on opposite sides of the longitudinal axis L.The stop members 1140 a, 1140 b define substantially flat/planaraxially-facing surfaces 1142 that are arranged substantially co-planarwith one another and with the planar end surface 1106 of the cuttingblock 1102, and which are also arranged substantially perpendicular tothe cutting plane of the first cutting blade 1112. As will be discussedbelow, the flat/planar surfaces 1142 of the stop members 1140 a, 1140 band the planar end surface 1106 of the cutting block 1102 serve to limitthe penetration depth of the vertical cut C_(VA) to prevent the cuttingblade 1112 from cutting too deep into the anterior tibial eminence 14_(A). Although the stop members 1140 a, 1140 b have been illustrated anddescribed as having a particular configuration, it should be understoodthat other structures and means for limiting travel of the anteriorchisel 1100 and the bone penetration depth of the cutting blade 1112 arealso contemplated including, for example, shoulder portions, flangeportions, lip portions, step portions, interference portions, or anyother structure suitable to limit the travel of the anterior chisel 1100and the bone penetration depth of the cutting blade 1112 into proximaltibia 12.

In a further embodiment, the anterior chisel 1100 includes a stop memberor shoulder 1150 defining an axially-facing edge or end surface 1152(i.e., facing a direction generally along longitudinal axis L). Theaxially-facing edge or end surface 1152 may be curved or contoured forabutment against a corresponding curved/contoured/irregular anteriorsurface of the proximal tibia 12, or may alternatively define asubstantially flat/planar axially-facing edge or end surface.Additionally, although the shoulder 1150 has been illustrated asextending continuously across the entire width of the cutting block1102, it should be understood that the shoulder 1150 may alternativelyextend across less than the entire width of the cutting block 1102and/or my extending discontinuously across the width of the cuttingblock 1102. As will be discussed below, the axially-facing edge or endsurface 1152 of the shoulder 1150 serves to limit the bone penetrationdepth of the horizontal cut C_(HA) to prevent the cutting blade 1122from cutting too deep into the anterior tibial eminence 14 _(A).Although the or shoulder 1150 has been illustrated and described ashaving a particular configuration, it should be understood that otherstructures and means for limiting travel of the anterior chisel 1100 andthe bone penetration depth of the cutting blade 1122 are alsocontemplated including, for example, flange portions, lip portions, stepportions, interference portions, or any other stop structure suitable tolimit the travel of the anterior chisel 1100 and the bone penetrationdepth of the cutting blade 1122 into proximal tibia 12.

Referring to FIGS. 62-64, reference will now be made to techniques forusing the anterior chisel 1100 to form both vertical and horizontal cutsC_(VA), C_(HA) along the anterior portion 14 _(A) of the tibial eminence14 for ultimate removal of the anterior portion 14 _(A) to providesufficient clearance for receipt of a tibial implant. However, it shouldbe understood that other techniques for using the anterior chisel 1100other than those specifically described herein are also contemplated.

Referring specifically to FIGS. 62A, 63A and 64A, shown therein is thestep of forming a vertical anterior cut C_(VA) along the anterior tibialeminence 14 _(A) using the anterior chisel 1100. The anterior chisel1100 is initially positioned above and generally aligned with theanterior tibial eminence 14 _(A), with the longitudinal axis L of theelongate shaft 1104 arranged generally parallel with the anatomicmechanical axis 13 of the proximal tibia 12. The planar guide/alignmentsurfaces 1132 defined by the axial projections 1130 a, 1130 b are thenpositioned in contact with the anterior surface S_(A) of the proximaltibia 12, and the cutting edge 1116 of the first cutting blade 1112 ispositioned adjacent the superior surface of the anterior tibial eminence14 _(A). Additionally, the cut reference marks/lines M (FIGS. 59B/60B)previously formed along the vertical medial and lateral resection cutsC_(VM), C_(VL) and across the superior surface of the anterior tibialeminence 14 _(A) (using the tibia size template 1000) are used as analignment/verification aid prior to and during formation of the verticalanterior cut C_(VA). As indicated above, the reference marks M representthe ideal location for the vertical anterior cut C_(VA), and are used asa check/verification via alignment of the cutting edge 1116 of the firstcutting blade 1112 with the reference marks M.

An axial cutting force F is then applied to the elongate shaft 1104which is transmitted to the cutting block 1102 and the first cuttingblade 1112 to form the vertical anterior cut C_(VA) along the anteriortibial eminence 14 _(A) (FIG. 64A). During formation of the verticalanterior cut C_(VA), the planar guide/alignment surfaces 1132 defined bythe axial projections 1130 a, 1130 b slide along the anterior surfaceS_(A) of the proximal tibia 12 to guide the anterior chisel 1100 alongthe proper cutting plane and to maintain the anterior chisel 1100 in agenerally parallel relationship with the anatomic mechanical axis 13 ofthe proximal tibia 12. Furthermore, displacement of the anterior chisel1100 is limited by abutment of the flat/planar stop surfaces 1142defined by the feet 1140 a, 1140 b and the planar end surface 1106 ofthe cutting block 1102 against the horizontal planar surfaces of themedial and lateral resections R_(M), R_(L) on either side of the tibialeminence 14. Notably, the penetration depth of the first cutting blade1112 is limited by such abutment so as to prevent the first cuttingblade 1112 from cutting too deep into the anterior tibial eminence 14_(A) and potentially weakening the remaining portion of the tibialeminence 14. The penetration depth of the first cutting blade 1112 ispreferably limited to the plane defined by the flat/planar stop surfaces1142 of the feet 1140 a, 1140 b and the planar end surface 1106 of thecutting block 1102 (which corresponds to the resection plane defined bythe planar horizontal surfaces of the medial and lateral resectionsR_(M), R_(L) on either side of the tibial eminence 14).

As should be appreciated, the location of the vertical anterior cutC_(VA) along the anterior tibial eminence 14 _(A) in theanterior-posterior direction is determined by the cut referencemarks/lines M (FIGS. 59B/60B) previously formed along the verticalmedial and lateral resection cuts C_(VM), C_(VL) and across the superiorsurface of the anterior tibial eminence 14 _(A) using the tibia sizetemplate 1000, and are used as an alignment/verification aid prior toand during formation of the vertical anterior cut C_(VA). In analternative embodiment, the location of the vertical anterior cut C_(VA)along the anterior tibial eminence 14 a is determined by the offsetdistance d₁ between the planar guide/alignment surfaces 1132 defined bythe axial projections 1130 a, 1130 b and the cutting plane defined bythe first cutting blade 1112. As should also be appreciated, theanterior chisel 1100 may be designed with the appropriate offsetdistance d₁ to accommodate for a desired anterior-posterior location ofthe vertical anterior cut C_(VA). Additionally, a set of anteriorchisels 1100 may be provide having different offset distances d₁ toaccommodate for varying anterior-posterior locations of the verticalanterior cut C_(VA). In the illustrated embodiment, the anterior chisel1100 is configured to provide a vertical anterior cut C_(VA) along theanterior tibial eminence 14 _(A) that is substantially vertical andparallel with the anatomic mechanical axis 13 of the tibia, andsubstantially perpendicular to the vertical surfaces of the medial andlateral resections R_(M), R_(L). However, other embodiments are alsocontemplated where the vertical anterior cut C_(VA) may be taperedrelative to a true vertical orientation, angled either in asuperior-inferior direction or a medial-lateral direction (i.e.,internal/external rotation).

Referring to FIGS. 62B, 63B and 64B, shown therein is the step offorming a horizontal anterior cut C_(HA) along the anterior tibialeminence 14 _(A) using the anterior chisel 1100. The anterior chisel1100 is initially positioned anterior to and generally aligned with theanterior tibial eminence 14 _(A), with the longitudinal axis L of theelongate shaft 1104 oriented generally perpendicular to the anatomicmechanical axis 13 of the proximal tibia 12. The planar guide/alignmentsurfaces 1134 defined by the axial projections 1130 a, 1130 b are thenpositioned in contact with the horizontal planar surfaces of the medialand lateral resections R_(M), R_(L) on either side of the tibialeminence 14, and the cutting edge 1126 of the second cutting blade 1122is positioned in contact with the anterior surface of the anteriortibial eminence 14 _(A).

An axial cutting force F is then applied to the elongate shaft 1104which is transmitted to the cutting block 1102 and the second cuttingblade 1122 to form the horizontal anterior cut C_(HA) along the anteriortibial eminence 14 _(A) (FIG. 64A). During formation of the horizontalanterior cut C_(HA), the planar guide/alignment surfaces 1134 defined bythe axial projections 1130 a, 1130 b slide along the horizontal planarsurfaces of the medial and lateral resections R_(M), R_(L) on eitherside of the tibial eminence 14 to guide the anterior chisel 1100 alongthe proper cutting plane and to maintain the anterior chisel 1100 in agenerally perpendicular orientation relative to the anatomic mechanicalaxis 13 of the proximal tibia 12. Furthermore, displacement of theanterior chisel 1100 is limited by abutment of the axially-facing edgeor end surface 1152 defined by the shoulder 1150 against the anteriorsurface S_(A) of the proximal tibia 12. Notably, the penetration depthof the second cutting blade 1122 is limited by such abutment so as toprevent the second cutting blade 1122 from cutting too deep into theanterior tibial eminence 14 _(A) and potentially weakening the remainingportion of the tibial eminence 14. The penetration depth of the secondcutting blade 1122 is preferably limited to the plane defined by theplanar end surface 1106 of the cutting block 1102.

As should be appreciated, the penetration depth of the horizontalanterior cut C_(HA) in the anterior-posterior direction is determined bythe offset distance d₂ between the axially-facing edge or end surface1152 defined by the shoulder 1150 and the distal cutting edge 1126defined by the second cutting blade 1122 (with the cutting edge 1126preferably aligned with the planar end surface 1106 of the cutting block1102). As should also be appreciated, the anterior chisel 1100 may bedesigned with the appropriate offset distance d₂ to accommodate for adesired penetration depth of the second cutting blade 1122 in ananterior-posterior direction to form the horizontal anterior cut C_(HA).The penetration depth of the second cutting blade 1122 is preferablydetermined such that the horizontal anterior cut C_(HA) just intersectsthe vertical anterior Cut C_(VA) but does not extend significantlybeyond the vertical anterior cut C_(VA). Additionally, a set of anteriorchisels 1100 may be provide having different offset distances d₂ toaccommodate for varying penetration depths of the second cutting blade1122 in an anterior-posterior direction to form the appropriatehorizontal anterior cut C_(HA). In the illustrated embodiment, theanterior chisel 1100 is configured to provide a horizontal anterior cutC_(HA) along the anterior tibial eminence 14 _(A) that is substantiallyparallel and co-planar with the horizontal planar surfaces of the medialand lateral resections R_(M), R_(L) on either side of the tibialeminence 14. However, other embodiments are also contemplated where thehorizontal anterior cut C_(HA) may be tapered relative to the horizontalplanar surfaces of the medial and lateral resections R_(M), R_(L).

Referring to FIG. 64C, upon formation of the vertical anterior cutC_(VA) and the horizontal anterior cut C_(HA), the bone fragmentdefining the anterior tibial eminence 14 _(A) may be removed to therebycomplete the anterior resection R_(A), which in combination with themedial and lateral resections R_(M), R_(L) provides sufficient clearancefor installation of a tibial implant onto the resected proximal tibia12. Additionally, the antero-medial and antero-lateral corners of thetibial eminence 14 shown in FIG. 64C can be rounded to form eminenceradii along the corners (FIG. 68). The eminence radii generally serve toprovide additional clearance for receipt of the installed tibialimplant, and are made by trimming the sharp antero-medial andantero-lateral eminence corners with a rongeur tool or other bonecutting/contouring instruments. Alternatively, the eminence radii may beformed by cutting die features incorporated into the first cutting blade1112, the cutting block 1100 or, in other embodiments, the keel cavityformation instrument 1200 illustrated and described below.

As should now be appreciated, the anterior chisel 1100 can be used toform both the vertical anterior cut C_(VA) and the horizontal anteriorcut C_(HA) to resect the anterior tibial eminence 14 _(A), as opposed tousing two separate cutting instruments to form these cuts. Additionally,the anterior chisel 1100 includes built-in alignment and guide featuresthat serve to properly align and guide the cutting blades 1112, 1122 toform the vertical and horizontal cuts C_(VA), C_(HA), and also includedbuilt-in stop features that limit the bone penetration depth of thevertical and horizontal cuts C_(VA), C_(HA) to prevent the cuttingblades 1112, 1122 from cutting too deep into the anterior tibialeminence 14 _(A) which might otherwise weaken the remaining portion ofthe tibial eminence 14 and risk a tibial eminence fracture. Thesebuilt-in features significantly reduce the risks normally associatedwith resection of the anterior tibial eminence 14 _(A).

M. Keel Cavity Formation Instrument

Referring to FIGS. 65-67, shown therein is a keel cavity formationinstrument 1200 according to one form of the present invention. As willbe discussed in greater detail below, the keel cavity formationinstrument 1200 is used to form a keel cavity including one or moreslots/openings in the medial and lateral resected regions R_(M), R_(L)and the anterior resected region R_(A) of the proximal tibia 12 (FIGS.71A-71C), with the slots/openings sized and shaped to receive keels orother projections extending from the tibial implant to be installed ontothe proximal tibia 12.

In the illustrated embodiment, the keel cavity formation instrument 1200is configured to form various portions of the keel cavity in multiplesteps to lower the maximum input or impaction force that would otherwisebe necessary if the entire keel cavity were formed simultaneously in asingle step. Forming the keel cavity in multiple steps also allowsportions of the keel cavity to be formed via an input/impaction forceexerted along the anatomic mechanical axis of the tibia (which is thepreferred direction of the input/impaction force to minimize potentialharmful effects on the tibia such as a tibial fracture), and also allowsthe portions of the keel cavity that must be formed via an obliqueinput/impaction force (a force exerted at an angle relative to theanatomic mechanical axis of the tibia) to be formed separately, therebyreducing the extent of the oblique input/impaction force necessary toform the overall keel cavity. Additionally, portions of the keel cavityare formed via drilling or boring, thereby further reducing theinput/impaction force necessary to form the overall keel cavity.

The keel cavity formation instrument 1200 generally includes a main body1210, a vertical punch handle 1230 rigidly connected to the main body1210 and extending along a vertical punch axis A₁ (FIG. 67), a keelpunch plate 1240 removably attached to the main body 1210, an angledpunch handle 1250 movably connected to the main body 1210 and extendingalong an angled punch axis A₂ (FIG. 67), an angled keel punch blade 1260(FIG. 70B) extending from the angled punch handle 1250 and also arrangedalong the angled punch axis A₂, and a drill bit 1270 displaceable alongdrill guide passages formed in the angled punch handle 1250 and the mainbody 1210. Additionally, the keel cavity formation instrument 1200 isused in association with a tibial baseplate trial 1280 attached to theresected proximal tibia 12 which serves as both a gauge and afoundation/guide for the keel cavity formation instrument 1200. Detailsregarding each of these elements will be set forth below.

In the illustrated embodiment, the main body 1210 generally includes anangled passage 1212 (FIG. 66) extending therethrough along the angledpunch axis A₂, and a pair of drill guide passages or barrels 1214 a,1214 b (FIG. 66) extending along guide axes arranged generally parallelwith the angled punch axis A₂ and arranged symmetrically on oppositessides of the angled punch axis A₂ and the angled passage 1212. The drillguide passages or barrels 1214 a, 1214 b are sized and configured toguidingly receive a proximal guide shaft portion 1272 a of the drill bit1270 therethrough for guiding displacement of the drill bit 1270 in adirection generally parallel with the angled punch axis A₂. In theillustrated embodiment of keel cavity formation instrument 1200, theangled punch axis A₂ is oriented at an offset angle α (FIG. 67) ofapproximately 20° relative to the vertical punch axis A₁. However, itshould be understood that other offset angles α between the angled punchaxis A₂ and the vertical punch axis A₁ are also contemplated, includingoffset angles α greater than 20° or offset angles α less than 20°.

The main body 1210 further includes a pair of transverse flanges ortongues 1216 a, 1216 b (FIG. 66) extending from opposite sides of aninferior portion of the main body 1210 in a medial-lateral direction,and a fastener or lock member 1218 extending through an opening (notshown) in an anterior portion of the main body 1210 and arranged alongan axis generally parallel with the angled punch axis A and configuredto releasably attach the keel punch plate 1240 to the main body 1210.The main body 1210 also defines a visualization window 1220 extendingtransversely therethrough and positioned in communication with theangled passage 1212 to provide visualization of the angled punch handle1250 positioned in the angled passage 1212, and a visualization window1222 extending transversely therethrough and positioned in communicationwith the drill guide passages 1214 a, 1214 b and the angled passage 1212to provide visualization of the angled keel punch blade 1260 positionedin the angled passage 1212 and the drill bit 1270 positioned in eitherof the drill guide passages 1214 a, 1214 b. The fastener or lock member1218 includes a shaft 1224 having a distal end portion 1224 a configuredfor engagement/disengagement within an opening 1248 in the keel punchplate 1240, and also having a proximal head portion 1224 b extendingfrom a superior surface of the main body 1210. The fastener or lockmember 1218 further includes a lever or handle 1228 extendingtransversely from the proximal head portion 1224 b and configured tofacilitate rotation of the lock member 1218 and engagement/disengagementof the distal end portion 1224 a within the opening 1248.

In the illustrated embodiment, the vertical punch handle 1230 generallyincludes an axial shaft portion 1232 extending generally along thevertical punch axis A₁ and having a distal end connected to the mainbody 1210 and a proximal end connected to a proximal handle portion orimpaction plate 1234 which defines a substantially flat/planar superiorimpaction surface 1234 a. As indicated above, the vertical punch handle1230 is rigidly connected to the main body 1210. However, in alternativeembodiments, the vertical punch handle 1230 may be removably and/ormovably attached to the main body 1210. As should be appreciated, theflat/planar superior impaction surface 1234 a of the impaction plate1234 is configured for receipt of an axial force F₁, such as animpaction force, applied to the impaction plate 1234 in a directiongenerally along the vertical punch axis A₁. The impaction force F₁ istransmitted along the axial shaft portion 1232, through the main body1210, and transmitted to the keel punch plate 1240 to drive a pair ofkeel formation wings or fins 1244 a, 1244 b of the keel punch plate 1240into the medial and lateral resected regions R_(M), R_(L), of theproximal tibia 12. Although the axial force F₁ is illustrated anddescribed as being applied to the impaction plate 1234 (e.g., via amallet), other structures and techniques for applying the axial force F₁to the keel formation instrument 1200 are also contemplated including,for example, via a slap hammer coupled to the main body portion 1210 orconnected directly to the keel punch plate 1240.

In the illustrated embodiment, the keel punch plate 1240 generallyincludes a generally flat plate portion 1242 including a pair of keelformation wings or fins 1244 a, 1244 b extending from an inferiorsurface 1242 a of the plate portion 1242. When the keel punch plate 1240is attached to the main body 1210 and the keel formation instrument 1200is properly positioned relative to the proximal tibia 12, the keelformation fins 1244 a, 1244 b are arranged on opposite sides of thevertical punch axis A₁ and include fin lengths that are outwardlytapered relative to one another in an anterior-posterior direction (FIG.71A). Additionally, as illustrated in FIG. 67, the keel formation fins1244 a, 1244 b each include a posterior surface 1245 a extendinggenerally along the vertical punch axis A₁, an anterior surface 1245 bextending generally along the angled punch axis A₂, and an inferiorsurface 1245 c extending from the posterior surface 1245 a to theanterior surface 1245 b and arranged generally perpendicular to theanterior surface 1245 b. In this arrangement, the keel formation fins1244 a, 1244 b each defines a generally pointed distal-most corner oredge 1245 d that facilitates penetration of the keel formation fins 1244a, 1244 b into tibial bone. As shown in FIG. 71A, the keel formationfins 1244 a, 1244 b are sized and shaped to form medial and lateral keelreceiving slots S_(M), S_(L) in the medial and lateral resected regionsR_(M), R_(L) of the proximal tibia 12.

The generally flat plate portion 1242 also includes a pair of L-shapedconnection flanges 1246 a, 1246 b extending from a superior surface 1242b of the plate portion 1242 and each defining a transversely extendinggroove 1247 sized and configured for receipt of the transverse flangesor tongues 1216 a, 1216 b of the main body 1210 therein to removablyengage the keel punch plate 1240 to the main body 1210. The generallyflat plate portion 1242 also defines an opening 1248 configured toreceive the distal end portion 1224 a of the lock member 1218 associatedwith the main body 1210 to removably lock the keel punch plate 1240 tothe main body 1210. Additionally, the generally flat plate portion 1242of the keel punch plate 1240 also defines an open region 1249 sized andconfigured to receive the tibial eminence 14 therein when the keel punchplate 1240 is positioned on the resected proximal tibia 12, and which isalso sized and configured to receive the angled keel punch blade 1260and the distal cutting portion of the drill bit 1270 therethrough duringformation of the anterior keel slot and openings in the anterior regionof the resected proximal tibia 12, further details of which will be setforth below. As should be appreciated, the keel punch plate 1240 is amodular feature of the keel cavity formation instrument 1200 that can beeasily removed from the main body 1210 of the instrument and replacedwith a different keel punch plate 1240 having a different size and/ordifferent keel formation fins 1244 a, 1244 b. It should be furtherappreciated that multiple keel punch plates 1240 having different sizesand/or fin features can be provided in a kit or set, thereby allowingfor the selection of a keel punch plate 1240 having the appropriatesize/fin features to accommodate the specific requirements of aparticular knee arthroplasty procedure.

In the illustrated embodiment, the angled punch handle 1250 generallyincludes an axial shaft portion 1252 extending generally along theangled punch axis A₂ and movably positioned in the angled passage 1212in the main body 1210 for guided axial movement or displacementgenerally along the angled punch axis A₂ relative to the main body 1210.The axial shaft portion 1252 includes a distal end connected to theangled keel punch blade 1260 and a proximal end connected to a proximaldrill guide plate 1254, which in turn defines a pair of drill guidepassages 1254 a, 1254 b extending along axes positioned on oppositesides of the angled punch axis A₂ and arranged generally parallel withthe angled punch axis A₂. The drill guide passages 1254 a, 1254 b aresized and configured to guidingly receive a proximal guide shaft portion1272 a of the drill bit 1270 therethrough for guiding displacement ofthe drill bit 1270 in a direction generally parallel with the angledpunch axis A₂. An impaction plate 1256 extends from a superior surfaceof the drill guide plate 1254 and defines a substantially flat/planarsuperior impaction surface 1256 a. As should be appreciated, theflat/planar superior impaction surface 1256 a of the impaction plate1256 is configured for receipt of an axial force F₂, such as animpaction force, applied to the impaction plate 1256 in a directiongenerally along the angled punch axis A₂. The impaction force F₂ istransmitted along the axial shaft portion 1252 and is transmitted to theangled keel punch blade 1260 to drive the angled keel punch blade 1260into the anterior resected region R_(A) of the proximal tibia 12.Although the axial force F₂ is illustrated and described as beingapplied to the impaction plate 1256 (e.g., via a mallet), otherstructures and techniques for applying the axial force F₂ to the angledpunch handle 1250 are also contemplated including, for example, via aslap hammer coupled to the axial shaft portion 1252 or connecteddirectly to the angled keel punch blade 1260. The angled punch handle1250 further includes a biasing member or spring 1258 extending aboutthe axial shaft portion 1252 and positioned within the angled passage1212 in the main body 1210 to bias the angled punch handle 1250 (and theangled keel punch blade 1260) in an axial direction generally along theangled punch axis A₂ toward a superior or retracted position forprotection of the cutting edges of the angled keel punch blade 1260during periods of non-use.

In the illustrated embodiment, the angled keel punch blade 1260generally includes a distal keel formation blade 1262 arranged generallyalong the angled punch axis A₂. When the keel formation instrument 1200is properly positioned relative to the proximal tibia 12, the distalkeel formation blade 1262 includes a blade length that generally extendsin a medial-lateral direction and transverse to the lengths of the keelformation fins 1244 a, 1244 b on the keel punch plate 1240. The distalkeel formation blade 1262 also defines a generally pointed distal-mostcorner or edge 1262 a that facilitates penetration of the keel formationblade 1262 into tibial bone. As shown in FIG. 71B, the distal keelformation blade 1262 is sized and shaped to form an anterior keelreceiving slot S_(A) in the anterior resected region R_(A) of theproximal tibia 12 positioned anterior to the tibial eminence 14 andextending generally along the angled punch axis A₂. As indicated above,the angled keel punch blade 1260 is connected to the distal end of theangled punch handle 1250. Alternatively, the angled keel punch blade1260 and the angled punch handle 1250 may be formed as unitary,single-piece element. Additionally, when the angled punch handle 1250 ispositioned in a retracted or non-actuated position (FIG. 70A), thedistal keel formation blade 1262 is retracted into the angled passage1212 in the main body 1210 and is fully retracted inwardly beyond theinferior surface of the tibial baseplate trial 1280. However, when theangled punch handle 1250 is positioned in an extended or actuatedposition (FIG. 70B), the distal keel formation blade 1262 extends out ofthe angled passage 1212 in the main body 1210 and projects outwardlybeyond the inferior surface of the tibial baseplate trial 1280 to formthe anterior keel receiving slot S_(A) in the anterior resected regionR_(A) of the proximal tibia 12.

In the illustrated embodiment, the drill bit 1270 extends along alongitudinal axis L and generally includes a drill shaft 1272 having aproximal guide shaft portion 1272 a and distal shaft portion 1272 b. Theproximal guide shaft portion 1272 a is sized and configured for guideddisplacement in a direction generally parallel with the angled punchaxis A₂ along the drill guide passages 1254 a, 1254 b in the proximaldrill guide plate 1254 of the angled punch handle 1250, and along thedrill guide barrels 1214 a, 1214 b defined through the main body 1210 ofthe keel cavity formation instrument 1200. The drill bit 1270 alsoincludes a proximal head 1274 including connection portion 1274 aconfigured for rotational coupling with a rotary driver (e.g., a rotarymotor or a torque application handle) to facilitate the application of arotational force or torque onto the drill bit 1270, and an enlarged stopportion or ring 1274 b defining a shoulder 1274 c configured to abut thesuperior surface defined by the drill guide plate 1254 of the angledpunch handle 1250 to limit penetration of the distal cutting portion1276 of the drill bit 1270 into tibial bone. The distal cutting portion1276 extends axially from the distal shaft portion 1272 b and definesone or more cutting flutes 1278 configured for drilling into tibialbone, and may also defined a pointed distal tip to facilitate initialpenetration into tibial bone. When the keel cavity formation instrument1200 is properly positioned relative to the proximal tibia 12, the drillbit 1270 may be inserted through one of the drill guide passages 1254 a,1254 b in the proximal drill guide plate 1254 and a corresponding one ofthe drill guide barrels 1214 a, 1214 b in the main body 1210, with thedistal cutting portion 1276 extending outwardly beyond the inferiorsurface of the tibial baseplate trial 1280 for drilling into theproximal tibia 12. As indicated above, abutment of the shoulder 1274 cdefined by the enlarged stop portion or ring 1274 b of the drill bit1270 limits penetration/drill depth of the distal cutting portion 1276into the proximal tibia 12. In one embodiment, the penetration depth ofthe drill bit 1270 into the proximal tibia 12 is approximately equal tothe penetration depth of the keel formation blade 1262 into the proximaltibia 12.

As shown in FIG. 71C, the drill bit 1270 is used to form medial andlateral keel receiving openings O_(M), O_(L) in the medial and lateralresected regions R_(M), R_(L) of the proximal tibia 12, with each of theopenings arranged on opposite sides of the tibial eminence 14 andextending generally along the angled punch axis A₂. In the illustratedembodiment, the drill bit 1270 is used to form the medial and lateralkeel receiving openings O_(M), O_(L) when the angled punch handle 1250and the distal keel formation blade 1262 are positioned in an extendedor actuated position (FIG. 70C) to provide additional stability andsupport to the keel cavity formation instrument 1200 during the drillingoperations. In one embodiment, the angled punch handle 1250 and thedistal keel formation blade 1262 are maintained in the extended oractuated position via friction forces exerted onto the distal keelformation blade 1262 by the surrounding bone. However, other embodimentsare also contemplated wherein the angled punch handle 1250 and thedistal keel formation blade 1262 may be maintained in the extended oractuated position via a positive catch or lock mechanism. Additionally,in other embodiments, the drilling operations may be performed when theangled punch handle 1250 and the distal keel formation blade 1262 arepositioned in the retracted or non-actuated position.

Referring to FIG. 68, in the illustrated embodiment, the tibialbaseplate trial 1280 acts as both a datum reference for the formation ofportions of a keel cavity in the proximal tibia 12 and as a tibialgauge, the details of which will become apparent below. The tibialbaseplate trial 1280 generally comprises a plate 1282 definingsubstantially flat/planar superior and inferior surfaces 1284 a, 1284 band an outer peripheral surface or edge 1286 defining an outer perimeteror profile that generally matches/corresponds to the outer profile ofthe resected proximal tibia 12 (i.e., the outer peripheral surface oredge 1286 is generally alignable with the outer peripheral edge of theresected proximal tibia 12). The plate 1282 may also be provided with ananterior plate extension portion 1282 a defining a visualization window1288 extending therethrough to allow visual inspection/alignment of theanterior region 1286 a of the outer peripheral surface 1286 with theanterior peripheral edge of the resected proximal tibia 12. The anteriorplate extension portion 1282 a provides additional stability and supportto the keel cavity formation instrument 1200 during formation of thekeel slots/openings in the proximal tibia 12 to aid in counteracting theimpaction forces F₁ and F₂ applied to the keel cavity formationinstrument 1200, and may also provide other benefits and advantages.

Additionally, in the illustrated embodiment, the plate 1282 defines acentrally positioned U-shaped slot 1290 extending therethrough betweenthe superior and inferior surfaces 1284 a, 1284 b and having an open endat the posterior peripheral surface 1286 and extending in aposterior-anterior direction. The slot 1290 defines an open inner regionof the plate 1282 that is sized and shaped to receive the tibialeminence 14 therein when the tibial baseplate trial 1280 is positionedon the resected proximal tibia 12. The plate 1282 also defines a pair ofpassages 1292 a, 1292 b extending therethrough between the superior andinferior surfaces 1284 a, 1284 b and positioned along medial and lateralportions of the plate 1282, respectively. The passages 1292 a, 1292 bare sized to receive fasteners or pins (not shown) to attach the tibialbaseplate trial 1280 to the resected proximal tibia 12. The plate 1282further defines a pair of slots or slits 1294 a, 1294 b extendingtherethrough between the superior and inferior surfaces 1284 a, 1284 band positioned along medial and lateral portions of the plate 1282,respectively. The slots 1294 a, 1294 b inwardly taper toward one anotherin a posterior-anterior direction and are sized and positioned toreceive the keel formation fins 1244 a, 1244 b of the keel punch plate1240 during formation of the medial and lateral keel receiving slotsS_(M), S_(L) in the resected proximal tibia 12. The slots 1294 a, 1294 bare preferably sized and shaped for relatively close tolerance with thekeel formation fins 1244 a, 1244 b so as to guide the keel punch plate1240 generally along the vertical punch axis A₁ during themedial/lateral keel slot formation process. Additionally, the plate 1282defines an elongate opening 1296 extending therethrough between thesuperior and inferior surfaces 1284 a, 1284 b and positioned along ananterior portion of the plate 1282, and including a length extending ina medial-lateral direction and communicating with each of the slots 1294a, 1294 b. The elongate opening 1296 is sized and positioned to receivethe distal keel formation blade 1262 of the angled keel punch blade 1260and the distal cutting portion 1276 of the drill bit 1270 duringformation of the anterior keel receiving slot S_(A) and the medial andlateral keel receiving openings O_(M), O_(L) in the resected proximaltibia 12. The elongate opening 1296 need not be configured to guide theangled keel punch blade 1260 and the drill bit 1270 during the duringthe anterior keel slot and medial and lateral opening formation processsince these elements are guided by other features associated with thekeel cavity formation instrument 1200. Further, interior medial andlateral surfaces of the plate 1282 extending between the central slot1290 and the medial/lateral slots 1294 a, 1294 b define recesses orgrooves 1298 a, 1298 b, the purpose of which will be set forth belowwith regard to the anterior gauge 1300. As should be appreciated, thetibial baseplate trial 1280 is ambidextrous, which means that the tibialbaseplate trial 1280 can be flipped over and used in association withthe other knee. Accordingly, a single tibial baseplate trial 1280 can beused to perform knee arthroplasty procedures on both the right knee andthe left knee.

Referring collectively to FIGS. 68-71, having described the components,elements and features associated with the keel cavity formationinstrument 1200, reference will now be made to methods and techniquesfor forming a keel cavity (including slots and openings) in the resectedproximal tibia 12. However, it should be understood that other methodsand techniques regarding the use of the keel cavity formation instrument1200 are also contemplated.

Referring first to FIG. 68, the tibial baseplate trial 1280 is initiallypositioned atop the resected proximal tibia 12 with the tibial eminence14 positioned within the central U-shaped slot 1290, and with the planarinferior surface 1284 b resting on the substantially flat/planarresected surfaces of the proximal tibia 12. The position and orientationof the tibial baseplate trial 1280 on the resected proximal tibia 12 canthen be adjusted to generally align the outer peripheral surface or edge1286 of the plate 1282 with the outer peripheral edge of the resectedproximal tibia 12. As indicated above, the anterior peripheral edge ofthe resected proximal tibia 12 can be viewed through the visualizationwindow 1288 defined by the anterior plate extension portion 1282 a toaid in the alignment of the anterior surface or edge of the plate 1282with the anterior edge of the resected proximal tibia 12. If the outerperipheral surface or edge 1286 of the tibial baseplate trial 1280 doesnot properly align with the outer peripheral edge of the resectedproximal tibia 12, a tibial baseplate trial 1280 having a different sizecan be chosen for positioning and alignment on the resected proximaltibia 12. It should be understood that a kit or set of multiple tibialbaseplate trials 1280 having different sizes can be provided to aid inthe selection of an appropriately sized tibial baseplate trial 1280.Once a tibial baseplate trial 1280 having the correct size is found andis properly aligned on the resected proximal tibia 12 (e.g., properlypositioned and oriented), the plate 1282 can be connected/anchored tothe resected proximal tibia 12 by passing a pair of fasteners or pins(not shown) through the medial and lateral passages 1292 a, 1292 b andinto engagement with tibial bone.

Referring to FIGS. 69, 70A and 71A, the keel cavity formation instrument1200 is then positioned in a superior position above the tibialbaseplate trial 1280 and the keel formation fins 1244 a, 1244 b of thekeel punch plate 1240 are positioned in the corresponding slots 1294 a,1294 b in the plate 1282. With the vertical punch axis A₁ generallyaligned with the anatomic axis 13 of the tibia, an axial impaction forceF₁ is applied to the superior impaction surface 1234 a of the impactionplate 1234 to drive the keel formation fins 1244 a, 1244 b of the keelpunch plate 1240 into the medial and lateral resected regions R_(M),R_(L) of the proximal tibia 12, which in turn forms the medial andlateral keel receiving slots S_(M), S_(L) in the resected proximal tibia12 (FIG. 71A).

Referring to FIGS. 70B and 71B, an axial impaction force F₂ is thenapplied to the superior impaction surface 1256 a of the impaction plate1256 on the angled punch handle 1250 in a direction generally along theangled punch axis A₂ to drive the distal keel formation blade 1262 ofthe keel punch blade 1260 into the anterior resected region R_(A) of theproximal tibia 12, which in turn forms the anterior keel receiving slotS_(A) in the anterior resected region R_(A) of the proximal tibia 12(FIG. 71B).

Referring to FIGS. 70C and 71C, with the angled punch handle 1250 andthe distal keel formation blade 1262 remaining in the extended oractuated position (i.e., to provide additional stability and support tothe keel cavity formation instrument 1200), the drill bit 1270 isinserted through one of the drill guide passages 1254 a, 1254 b and acorresponding one of the drill guide barrels 1214 a, 1214 b and isdrilled into the proximal tibia 12 in a direction generally parallelwith the angled punch axis A₂ to form one of the medial and lateral keelreceiving openings O_(M), O_(L) in the medial and lateral resectedregions R_(M), R_(L) of the proximal tibia 12. The drill bit 1270 isthen inserted through the other of the drill guide passages 1254 a, 1254b and the corresponding drill guide barrel 1214 a, 1214 b and drilledinto the proximal tibia 12 in a direction generally parallel with theangled punch axis A₂ to form the other of the medial and lateral keelreceiving openings O_(M), O_(L) in the medial and lateral resectedregions R_(M), R_(L) of the proximal tibia 12 (FIG. 71C).

Following the formation of the medial and lateral keel receiving slotsS_(M), S_(L), the anterior keel receiving slot S_(A) and the medial andlateral keel receiving openings O_(M), O_(L), the keel cavity formationinstrument 1200 may be disengaged and removed from the tibial baseplatetrial 1280. However, the tibial baseplate trial 1280 is preferably leftanchored to the resected proximal tibia 12 to perform an anteriorgauging technique using the anterior gauge 1300 illustrated anddescribed below.

As should be appreciated, the medial and lateral keel receiving slotsS_(M), S_(L), the anterior keel receiving slot S_(A) and the medial andlateral keel receiving openings O_(M), O_(L) form an overall keel cavityin the resected proximal tibia 12 having a U-shaped configuration, andwith the keel receiving slots/openings sized, positioned and oriented toreceive or provide clearance for corresponding keels or otherprojections extending from a tibial implant (not shown) uponinstallation of the tibial implant onto the resected proximal tibia 12.As should also be appreciated, the keel cavity formation instrument 1200can be used in association with multiple sizes of proximal tibias andtibial implants, as well as both left and right hand proximal tibias andtibial implants, thereby reducing the need to provide multiple keelcavity formation instruments 1200 to accommodate various kneearthroplasty procedures. Additionally, the precision and accuracyoffered by the tibial baseplate trial 1280 when used as a controlleddatum reference and/or guide is desirable as it can help ensure thatthere is no mismatch conflict between the tibial eminence 14 and theportions of the U-shaped keel cavity when the tibial implant isinstalled onto the resected proximal tibia 12. Since the tibial implantwill mate or at least correspond/relate to both the tibial eminence 14and the portions of the U-shaped keel cavity, it can be important thatthese two features are positioned/oriented correctly relative to oneanother so that the tibial implant does not bind, become tilted, sit tooproud after installation onto the resected proximal tibia 12, orcompromise the remaining portion of the preserved tibial eminence 14.

As should be further appreciated, the keel cavity formation instrument1200 is configured to form various portions/sections of the overall keelcavity in multiple steps to thereby lower the maximum input or impactionforces that would otherwise be necessary if the entire keel cavity wereformed simultaneously in a single step, thereby lowering the risksassociated with tibial fractures via application of reduced input orimpaction forces. Additionally, forming the keel cavity in multiplesteps also allows various portions of the keel cavity (i.e., the medialand lateral keel receiving slots S_(M), S_(L)) to be formed via aninput/impaction force exerted generally along the anatomic mechanicalaxis of the tibia (i.e., generally along the vertical punch axis A₁),which is a preferred direction for application of the input/impactionforce, and also allows portions of the keel cavity (i.e., the anteriorkeel receiving slot S_(A)) that must be formed via an obliqueinput/impaction force (i.e., generally along the angled punch axis A₂)to be formed separately, thereby reducing the extent of the obliqueinput/impaction force necessary to form the overall keel cavity.Further, still other portions of the keel cavity are formed via drilling(i.e., the medial and lateral keel receiving openings O_(M), O_(L)),thereby further reducing the input/impaction force necessary to form theoverall keel cavity. Therefore, it should be apparent that the design ofthe keel cavity formation instrument 1200 provides several benefits andadvantages over conventional instruments and techniques.

N. Anterior Gauge

Referring to FIGS. 72A/72B, shown therein is an anterior gauge 1300according to one form of the present invention. As will be discussedbelow, in one embodiment, the anterior gauge 1300 is used in combinationwith the tibial baseplate trial 1280 to gauge/inspect various featuresand aspects associated with the resected anterior portion of the tibialeminence 14 (i.e., position, orientation, size and shape) relative tothe tibial baseplate trial 1280 after formation of the keel receivingslots/openings associated with the keel cavity in the resected proximaltibia 12. The anterior gauge 1300 is designed to check and verify theaccuracy of these features and aspects to ensure compatibility of theresected proximal tibia 12 with the selected tibial implant prior toinstallation of the tibial implant. However, it should be appreciatedthat in other embodiments, the anterior gauge 1300 may be used incombination with the tibial baseplate trial 1280 to gauge/inspectvarious features and aspects associated with the resected anteriorportion of the tibial eminence 14 (i.e., position, orientation, size andshape) to check and verify the accuracy of these features and aspectsprior to formation of the keel receiving slots/openings associated withthe keel cavity in the resected proximal tibia 12. Other embodimentsdirected to further uses of the anterior gauge 1300 with or without thetibial baseplate trial 1280 are also contemplated as falling within thescope of the present invention.

In the illustrated embodiment, the anterior gauge 1300 generallyincludes a connection portion 1302 and a handle portion 1304 extendingaxially from the connection portion 1302 along a longitudinal axis L.The connection portion 1302 is generally configured for removableconnection with the tibial baseplate trial 1280 and forabutment/engagement with the resected anterior portion of the tibialeminence 14. The handle portion 1304 is generally configured to aid inthe manipulation and handling of the anterior gauge 1300 and the tibialbaseplate trial 1280, and/or for attachment to an alignment rod or “uprod” (not shown), or potentially to other alignment devices or supportstructures.

In one embodiment, the connection portion 1302 is ambidextrous in thatit is configured for removable attachment to both a left handconfiguration of the tibial baseplate trial 1280 (FIGS. 73 and 74) and aright hand configuration of the tibial baseplate trial 1280 (formed byflipping the tibial baseplate trial 1280 over). To provide thisambidextrous capability, the connection portion 1302 includes a lefthand region 1310 configured for removable attachment to the left handconfiguration of the tibial baseplate trial 1280, and a right handregion 1312 configured for removable attachment to the right handconfiguration of the tibial baseplate trial 1280. In the illustratedembodiment, the left hand and right hand regions 1310, 1312 arepositioned on opposite superior/inferior portions of the connectionportion 1302, arranged general symmetric to one another relative to thelongitudinal axis L. As should be appreciated, the left hand and righthand regions 1310, 1312 of the connection portion 1302 that areremovably connectable with a corresponding left/right hand configurationof the baseplate trial 1280 are appropriately marked with “L” and “R”designations (FIGS. 74A and 74B) along a superior surface of theconnection portion 1302, and are also marked with a numeric range whichindicates the size of the tibial baseplate trial 1280 (i.e., “1-4” whichcorresponds to the size of the tibia implant) for which the connectionportion 1302 may be attached to. As should also be appreciated, thetibial baseplate trials 1280 are also appropriately marked with “L” and“R” designations along a superior surface of the plate 1282, as well asbeing marked with a numeric size number which indicates the size of thetibial baseplate trial 1280 and the corresponding size of the tibiaimplant.

The left hand and right hand regions 1310, 1312 of the connectionportion 1302 each include a pair of medial and lateral sections 1310 a,1310 b and 1312 a, 1312 b, respectively, which each include anaxially-facing posterior surface defining a detent mechanism or ball1314 extending therefrom. The detent mechanisms or balls 1314 are sizedand shaped for receipt within corresponding ones of the recesses/grooves1298 a, 1298 b formed along the interior medial and lateral surfaces ofthe tibial baseplate trial 1280 for removable attachment of theconnection portion 1302 with the tibial baseplate trial 1280.Additionally, the connection portion 1302 includes a pair of centralalignment members 1311 a, 1311 b positioned on opposite sides of thelongitudinal axis L and between the left hand and right hand regions1310, 1312 of the connection portion 1302. The central alignment members1311 a, 1311 b define opposite substantially flat/planar abutmentsurfaces configured for abutment against a corresponding superiorsurface of the tibial baseplate trial 1280. The connection portion 1302also defines a curved or contoured posterior-facing gauge surface 1316extending between the medial and lateral sections 1310 a, 1310 b, 1312a, 1312 b. The curved or contoured posterior-facing gauge surface 1316of the connection portion 1302 is sized and shaped for close-fittingabutment against the resected anterior portion of the tibial eminence 14(FIG. 74B).

In one embodiment, the handle portion 1304 includes a shaft portion 1320extending axially from an anterior surface of the connection portion1302, and a proximal gripping portion 1322 extending axially from theshaft portion 1320 and configured to be grasped and manipulated by auser. The proximal gripping portion 1322 further defines a series ofopenings 1324 sized and configured for optional receipt of an alignmentrod or “up rod” (not shown) or to other alignment devices or supportstructures.

Referring to FIGS. 73A and 73B, shown therein is the tibial baseplatetrial 1280 attached to the resected proximal tibia 12, with the tibialeminence 14 positioned within the central U-shaped slot 1290 of thebaseplate trial 1280, and with the planar inferior surface 1284 bresting on the substantially flat/planar resected surfaces of theproximal tibia 12. As should be appreciated, the anterior gauge 1300 maybe removably attached to the tibial baseplate trial 1280 to aid in themanipulation and handling of the baseplate trial 1280 relative to theresected proximal tibia 12 by positioning the appropriate left or righthand region 1310, 1312 of the connection portion 1302 into the anteriorelongate opening 1296 in the baseplate trial 1280 until the detentmechanisms or balls 1314 snap or click into the recesses/grooves 1298 a,1298 b formed along the interior medial and lateral surfaces of thebaseplate trial 1280. The position and orientation of the tibialbaseplate trial 1280 relative to the resected proximal tibia 12 can beadjusted to generally align the outer peripheral surface or edge 1286 ofthe plate 1282 with the outer peripheral edge of the resected proximaltibia 12 prior to anchoring of the baseplate trial 1280 to the proximaltibia. Additionally, the anterior gauge 1300 is used to check/verify theaccuracy and precision of various aspects and features associated withthe tibial eminence 14 (i.e., position, orientation, size and shape) viaa close-fitting arrangement between the curved or contouredposterior-facing gauge surface 1316 of the anterior gauge 1300 and theresected anterior portion of the tibial eminence 14. Notably, thischeck/verification can be conducted either before and/or after formationof the keel cavity in the resected horizontal surfaces of the proximaltibia 12. Additionally, the anterior gauge 1300 can be easily removedfrom the tibial baseplate trial 1280 to avoid interference withformation of the slots/opening associated with the keel cavity by simplypulling up on the handle portion 1304 in a generally vertical directionuntil the detent mechanisms or balls 1314 become disengaged from therecesses/grooves 1298 a, 1298 b in the tibial baseplate trial 1280.

Referring to FIGS. 74A and 74B, shown there is the anterior gauge 1300removably attached to the tibial baseplate trial 1280. As indicatedabove, the anterior gauge 1300 is removably attached to the tibialbaseplate trial 1280 by positioning the appropriate left or right handregion 1310, 1312 of the connection portion 1302 into the anteriorelongate opening 1296 in the tibial baseplate trial 1280 until thedetent mechanisms or balls 1314 snap or click into the recesses/grooves1298 a, 1298 b formed along the interior medial and lateral surfaces ofthe tibial baseplate trial 1280. At this point, the substantially flatplanar abutment surfaces defined by the central alignment members 1311a, 1311 b should abut against the superior surface of the tibialbaseplate trial 1280, and the curved or contoured posterior-facing gaugesurface 1316 of the connection portion 1302 should abut the resectedanterior portion of the tibial eminence 14 in a close-fittingarrangement (FIG. 74B). If these abutting surfaces appropriately matewith one another in a close fitting arrangement, the accuracy andprecision of the aspects and features of the tibial eminence 14 (i.e.,position, orientation, size and shape) in relation to tibia implant fithave been confirmed, and the baseplate trial 1280 can be removed fromthe proximal tibia 12 followed by final installation of the tibialimplant onto the prepared proximal tibia 12 in a conventional manner.However, if these abutting surfaces do not appropriately mate with oneanother, additional modifications to the tibial eminence 14 and/or otherportions of the resected proximal tibia 12 may be necessary prior toaccommodate for the installation of the tibial implant.

It should be understood that method steps disclosed herein may beperformed in any order regardless of the order in which they arepresented, discussed or illustrated, and that while a medial cut firstmethod may be preferable in some embodiments, the surgical techniquesprovided herein may be adapted for a lateral cut first method. It shouldalso be understood that any experiments, experimental examples, orexperimental results provided herein are intended to be illustrative ofthe present invention, and should not be construed to limit or restrictthe invention scope. Further, any theory, mechanism of operation, proof,or finding stated herein is meant to further enhance understanding ofthe present invention and is not intended to limit the present inventionin any way to such theory, mechanism of operation, proof, or finding.

In reading the claims, words such as “a”, “an”, “at least one”, and “atleast a portion” are not intended to limit the claims to only one itemunless specifically stated to the contrary. Additionally, when thelanguage “at least a portion” and/or “a portion” is used, the claims mayinclude a portion and/or the entire item unless specifically stated tothe contrary. Furthermore, when the term “distal” is used with respectto a structure, the term refers to the far end of the structure, andwhen the term “proximal” is used with respect to a structure, the termrefers to the near end of the structure. Moreover, the terms “superior”,“inferior”, “medial”, “lateral”, “anterior”, “posterior”, “up”, down”,“left”, “right”, “front”, “rear”, “horizontal” and “vertical” refer togeneral directions defined from a normal/upright view point lookingtoward the anterior region of the proximal tibia.

Various changes and modifications to the described embodiments describedherein will be apparent to those skilled in the art, and such changesand modifications can be made without departing from the spirit andscope of the invention and without diminishing its intended advantages.Additionally, while the invention has been illustrated and described indetail in the drawings and foregoing description, the same is to beconsidered illustrative and not restrictive in character, it beingunderstood that only selected embodiments have been shown and describedand that all changes, equivalents, and modifications that come withinthe scope of the inventions described herein or defined by the followingclaims are desired to be protected.

What is claimed is:
 1. Instrumentation for resection of the proximaltibia, comprising: a mounting base adapted for coupling to the proximaltibia; a cutting guide extending laterally from the mounting base andincluding a lateral guide channel arranged along a cutting plane anddimensioned to guide a cutting device along the cutting plane to form aresection cut in the proximal tibia; and an elongate pin interconnectedwith a mounting portion of the instrument and dimensioned for receiptwithin an opening in the proximal tibia, the elongate pin is offset fromthe lateral guide channel and positioned within the cutting plane,wherein the elongate pin is positioned to engage a cutting edge of thecutting device to thereby limit lateral displacement of the cuttingdevice along the cutting plane, wherein the elongate pin is pivotallyconnected to the mounting portion and pivots along the cutting plane,and wherein the elongate pin pivots about a pivot axis arrangedperpendicular to the cutting plane.
 2. The instrumentation of claim 1,wherein the elongate pin is positively connected to the mountingportion.
 3. The instrumentation of claim 2, wherein the elongate pin ismovably connected to the mounting portion.
 4. The instrumentation ofclaim 1, wherein the mounting portion to which the elongate pin isinterconnected is defined by the mounting base.
 5. The instrumentationof claim 1, wherein the elongate pin is pivotally connected to themounting portion by a pivot pin to provide pivotal movement of theelongate pin along the cutting plane.
 6. The instrumentation of claim 5,wherein the pivot axis is arranged perpendicular to the elongate pin. 7.The instrumentation of claim 1, wherein the mounting portion to whichthe elongate pin is pivotally connected is defined by the mounting base.8. The instrumentation of claim 1, wherein the elongate pin has acircular or square-shaped outer cross section.
 9. The instrumentation ofclaim 1, wherein the elongate pin has a tapered distal end to facilitateinsertion into the opening in the proximal tibia.
 10. Theinstrumentation of claim 1, further comprising: a cutting devicepositioned within the lateral guide channel of the cutting guide; andwherein the elongate pin comprises a protective guard positioned tolimit the lateral displacement of the cutting device within the lateralguide channel and to prevent cutting of the proximal tibia laterallybeyond the protective guard.
 11. The instrumentation of claim 1, whereinthe cutting guide includes superior and inferior guide plates definingthe lateral guide channel therebetween.
 12. The instrumentation of claim11, wherein a superior surface of the superior guide plate and aninferior surface of the inferior guide plate are tapered in a lateraldirection to provide increased visualization of the proximal tibia. 13.The instrumentation of claim 1, wherein the lateral guide channel opensonto a laterally facing end portion of the cutting guide.
 14. Theinstrumentation of claim 1, further comprising: a mount deviceconfigured for attachment to the proximal tibia; and wherein the mountdevice includes a reference surface extending along a reference planeand arranged to guide a cutting device along the reference plane tofacilitate formation of a first resection cut in the proximal tibia; andwherein the cutting plane of the cutting guide is arranged co-planarwith the reference plane when the mounting base is releasably locked tothe mount device to facilitate formation of a second resection cut inthe proximal tibia co-planar with the first resection cut.
 15. Theinstrumentation of claim 1, further comprising: a mount deviceconfigured for attachment to the proximal tibia; and wherein the mountdevice includes a planar reference member extending along a referenceplane; and wherein the cutting plane of the lateral guide channel isarranged parallel with the reference plane when the mounting base isreleasably locked to the planar reference member of the mount device.16. The instrumentation of claim 15, wherein the mounting base includesan elongate slot, and wherein the planar reference member of the mountdevice is positioned within the elongate slot and is releasably engagedwithin the elongate slot by a lock mechanism.
 17. The instrumentation ofclaim 16, wherein the lock mechanism comprises a clamping mechanism. 18.The instrumentation of claim 1, further comprising: a mount deviceconfigured for attachment to the proximal tibia; and wherein the mountdevice includes a planar reference member extending along a referenceplane; and wherein the cutting plane of the lateral guide channel andthe reference plane of the mount device are co-planar when the mountingbase is releasably locked to the planar reference member of the mountdevice.
 19. The instrumentation of claim 1, wherein no portion of theelongate pin is positioned laterally adjacent the guide channel.
 20. Theinstrumentation of claim 1, wherein the cutting edge of the cuttingdevice does not contact the elongate pin within the guide channel. 21.The instrumentation of claim 1, wherein the elongate pin includes amounting portion and an elongate pin portion extending therefrom;wherein the mounting portion of the elongate pin is pivotally connectedto the mounting portion of the mounting device; and wherein the elongatepin portion is positioned remote from the guide channel.
 22. Theinstrumentation of claim 21, wherein no portion of the elongate pinportion is positioned laterally adjacent the guide channel.
 23. Theinstrumentation of claim 21, wherein the cutting edge of the cuttingdevice does not contact the elongate pin portion within the guidechannel.
 24. The instrumentation of claim 1, wherein the cutting guideincludes superior and inferior guide plates defining the lateral guidechannel therebetween; wherein the lateral guide channel opens onto alaterally facing end portion of the cutting guide; and wherein asuperior surface of the superior guide plate and an inferior surface ofthe inferior guide plate are tapered in a lateral direction to thelateral facing end portion of the cutting guide to provide increasedvisualization of the proximal tibia.
 25. Instrumentation for resectionof the proximal tibia, comprising: a cutting device; a mount deviceconfigured for attachment to the proximal tibia and including a planarreference member extending along a reference plane; a mounting basereleasably lockable to the planar reference member of the mount device;a cutting guide extending laterally from the mounting base and includinga lateral guide channel arranged along a cutting plane and dimensionedto guide the cutting device along the cutting plane to form a resectioncut in the proximal tibia; and an elongate pin pivotally connected to amounting portion of the instrumentation and configured for pivotalmovement along the cutting plane, the elongate pin dimensioned forreceipt within an opening in the proximal tibia, the elongate pin isoffset from the lateral guide channel and positioned within the cuttingplane, wherein the elongate pin is positioned to engage a cutting edgeof the cutting device to thereby limit lateral displacement of thecutting device within the lateral guide channel along the cutting plane,wherein the elongate pin is pivotally connected to the mounting portionand pivots along the cutting plane, and wherein the elongate pin pivotsabout a pivot axis arranged perpendicular to the cutting plane.
 26. Theinstrumentation of claim 25, wherein the mounting base is releasablylocked to the mount device with the cutting plane arranged parallel withthe reference plane.
 27. The instrumentation of claim 25, wherein thecutting plane and the reference plane are co-planar when the mountingbase is releasably locked to the mount device.
 28. The instrumentationof claim 25, wherein the planar reference member is arranged to guidethe cutting device along the reference plane to facilitate formation ofa first resection cut in the proximal tibia; and wherein the cuttingplane of the cutting guide is arranged co-planar with the referenceplane when the mounting base is releasably locked to the planarreference member of the mount device to facilitate formation of a secondresection cut in the proximal tibia substantially co-planar with thefirst resection cut.
 29. Instrumentation for resection of the proximaltibia, comprising: a mounting base adapted for coupling to the proximaltibia; a cutting guide extending laterally from the mounting base andincluding a lateral guide channel arranged along a cutting plane anddimensioned to guide a cutting device along the cutting plane to form aresection cut in the proximal tibia; and an elongate pin interconnectedwith a mounting portion of the instrument and dimensioned for receiptwithin an opening in the proximal tibia, the elongate pin is offset fromthe lateral guide channel and positioned within the cutting plane,wherein the elongate pin is positioned to engage a cutting edge of thecutting device to thereby limit lateral displacement of the cuttingdevice within the lateral guide channel along the cutting plane, whereinthe elongate pin is pivotally connected to the mounting portion andpivots along the cutting plane, and wherein the elongate pin pivotsabout a pivot axis arranged perpendicular to the cutting plane. 30.Instrumentation for resection of the proximal tibia, comprising: acutting device; a mount device configured for attachment to the proximaltibia and including a planar reference member extending along areference plane; a mounting base releasably lockable to the planarreference member of the mount device; a cutting guide extendinglaterally from the mounting base and including a lateral guide channelarranged along a cutting plane and dimensioned to guide the cuttingdevice along the cutting plane to form a resection cut in the proximaltibia; and an elongate pin pivotally connected to a mounting portion ofthe instrumentation and configured for pivotal movement along thecutting plane, the elongate pin dimensioned for receipt within anopening in the proximal tibia, the elongate pin is offset from thelateral guide channel and positioned within the cutting plane, whereinthe elongate pin is positioned to engage a cutting edge of the cuttingdevice to thereby limit lateral displacement of the cutting devicewithin the lateral guide channel along the cutting plane, wherein theelongate pin is pivotally connected to the mounting portion and pivotsalong the cutting plane, and wherein the elongate pin pivots about apivot axis arranged perpendicular to the cutting plane.